Semiconductor device and method of manufacturing the same

ABSTRACT

A performance of a semiconductor device is improved. A semiconductor device includes two element portions and an interposition portion interposed between the two element portions. The interposition portion includes a p-type body region formed in a part of a semiconductor layer, the part being located between two trenches, and two p-type floating regions formed in two respective parts of the semiconductor layer, the two respective portions being located on both sides of the p-type body region via the two respective trenches. A lower end of the p-type floating region is arranged on a lower side with reference to a lower end of the p-type body region.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese Patent ApplicationNo. 2015-187817 filed on Sep. 25, 2015, the content of which is herebyincorporated by reference into this application.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a semiconductor device, and can be usedsuitably as, for example, a semiconductor device including an insulatedgate bipolar transistor (IGBT).

BACKGROUND OF THE INVENTION

As an IGBT with low on-resistance, a trench gate type IGBT has widelybeen used. An IE (injection enhancement)-type IGBT has been developed,the IE-type IGBT enabling to use an IE effect because an active cellconnected to an emitter electrode and an inactive cell region having afloating region are arranged alternately in a cell formation region. TheIE effect serves to increase the concentration of charges accumulated ina drift region by preventing holes from being discharged from theemitter electrode side when the IGBT is in an on state.

Japanese Patent Application Laid-Open Publication No. 2012-256839(Patent Document 1) discloses a technique in an IE-type trench gate IGBTin which each of linear unit cell regions provided in a cell formationregion includes a linear active cell region and linear inactive cellregions provided so as to sandwich the linear active cell region fromboth sides thereof.

Japanese Patent Application Laid-Open Publication No. 2013-140885(Patent Document 2) discloses a technique in an IE-type trench gate IGBTin which each of linear unit cell regions provided in a cell formationregion includes first and second linear unit cell regions, in which thefirst linear unit cell region has a linear active cell region, and inwhich the second linear unit cell region has a linear hole collectorcell region.

International Publication WO/2011/111500 (Patent Document 3) discloses atechnique in an insulated gate semiconductor device in which one or moresecond trenches each formed to be between first trenches adjacent toeach other and be parallel to the first trenches are formed, and inwhich a first conductor is buried in the second trench via an insulatingfilm.

SUMMARY OF THE INVENTION

A semiconductor device including an IGBT having an EGE-type(emitter-gate-emitter-type) active cell region is known as an IE-typetrench gate IGBT, such as the IE-type trench gate IGBT disclosed inPatent Document 2 described above.

The semiconductor device including the IGBT having the EGE-type activecell region has a smaller influence of a displacement current generatedin the active cell region on a gate potential in a switching operationwhen an inductance is connected as a load, than that of a semiconductordevice including an IGBT having a GG-type (gate-gate-type) active cellregion.

However, it is desirable for the semiconductor device including the IGBThaving the EGE-type active cell region to further improve a performanceas a semiconductor device such as the IE effect.

Other object and novel characteristics of the present invention will beapparent from the description of the present specification and theaccompanying drawings.

A semiconductor device according to the present first embodimentincludes two element portions each formed in a first semiconductor layerin each of two first regions arranged to be spaced from each other in afirst direction, and includes an interposition portion formed in thefirst semiconductor layer and interposed between the two elementportions in a second region located between the two first regions. Theinterposition portion includes a p-type body region formed in a part ofthe first semiconductor layer located between two trenches and twop-type floating regions formed in two respective parts of the firstsemiconductor layer located on both sides of the p-type body region viathe two respective trenches. Each of lower ends of the two p-typefloating regions are arranged to be lower than a lower end of the p-typebody region.

Also, according to another embodiment, a method of manufacturing asemiconductor device includes a step of forming an element portion in afirst semiconductor layer in each of two first regions arranged to bespaced from each other in a first direction and a step of forming aninterposition portion interposed between the two element portions formedin the two respective first regions in the first semiconductor layer ina second region located between the two first regions. The step offorming the interposition portion includes a step of forming a p-typebody region in a part of the first semiconductor layer located betweentwo trenches and a step of forming two p-type floating regions each intwo parts of the first semiconductor layer located on both sides of thep-type body region via the two respective trenches. Each of lower endsof the two p-type floating regions is arranged to be lower than a lowerend of the p-type body region.

According to an embodiment, a performance of a semiconductor device canbe improved.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a plan view of a semiconductor chip as a semiconductor deviceaccording to a first embodiment;

FIG. 2 is a plan view of a principal part of the semiconductor deviceaccording to the first embodiment;

FIG. 3 is a plan view of a principal part of the semiconductor deviceaccording to the first embodiment;

FIG. 4 is a cross-sectional view of a principal part of thesemiconductor device according to the first embodiment;

FIG. 5 is a cross-sectional view of a principal part illustrating a stepof manufacturing the semiconductor device according to the firstembodiment;

FIG. 6 is a cross-sectional view of a principal part illustrating a stepof manufacturing the semiconductor device according to the firstembodiment;

FIG. 7 is a cross-sectional view of a principal part illustrating a stepof manufacturing the semiconductor device according to the firstembodiment;

FIG. 8 is a cross-sectional view of a principal part illustrating a stepof manufacturing the semiconductor device according to the firstembodiment;

FIG. 9 is a cross-sectional view of a principal part illustrating a stepof manufacturing the semiconductor device according to the firstembodiment;

FIG. 10 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 11 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 12 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 13 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 14 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 15 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 16 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 17 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 18 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 19 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 20 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to the firstembodiment;

FIG. 21 is a cross-sectional view of a principal part of a semiconductordevice according to a first comparative example;

FIG. 22 is a plan view of a principal part of a semiconductor deviceaccording to a second comparative example;

FIG. 23 is a cross-sectional view of a principal part of thesemiconductor device according to the second comparative example;

FIG. 24 is a cross-sectional view illustrating a displacement currentpath at the time of turn-on in the semiconductor device according to thefirst comparative example so as to be overlapped;

FIG. 25 is a circuit diagram illustrating a displacement current path atthe time of turn-on in the semiconductor device according to the firstcomparative example;

FIG. 26 is a cross-sectional view illustrating a displacement currentpath at the time of turn-on in the semiconductor device according to thesecond comparative example so as to be overlapped;

FIG. 27 is a circuit diagram illustrating a displacement current path atthe time of turn-on in the semiconductor device according to the secondcomparative example;

FIG. 28 is a cross-sectional view illustrating a p-channel parasiticMOSFET in the semiconductor device according to the second comparativeexample;

FIG. 29 is a cross-sectional view of a principal part of thesemiconductor device according to the second comparative example;

FIG. 30 is a cross-sectional view of a principal part of thesemiconductor device according to the first embodiment;

FIG. 31 is a cross-sectional view illustrating a snubber circuit formedin the semiconductor device according to the first embodiment to beoverlapped;

FIG. 32 is an equivalent circuit diagram of an IGBT to which the snubbercircuit is connected;

FIG. 33 is a cross-sectional view of a principal part of a semiconductordevice according to a modification example of the first embodiment;

FIG. 34 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to themodification example of the first embodiment;

FIG. 35 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to themodification example of the first embodiment;

FIG. 36 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to themodification example of the first embodiment;

FIG. 37 is a cross-sectional view of a principal part illustrating astep of manufacturing the semiconductor device according to themodification example of the first embodiment;

FIG. 38 is a cross-sectional view of a principal part of a semiconductordevice according to a second embodiment;

FIG. 39 is a plan view of a principal part of a semiconductor deviceaccording to a third embodiment;

FIG. 40 is a cross-sectional view of a principal part of thesemiconductor device according to the third embodiment;

FIG. 41 is a plan view of a principal part of a semiconductor deviceaccording to a fourth embodiment;

FIG. 42 is a plan view of a principal part of the semiconductor deviceaccording to the fourth embodiment;

FIG. 43 is a cross-sectional view of a principal part of thesemiconductor device according to the fourth embodiment;

FIG. 44 is a cross-sectional view of a principal part of thesemiconductor device according to the fourth embodiment;

FIG. 45 is a cross-sectional view of a principal part of thesemiconductor device according to the first embodiment;

FIG. 46 is a circuit block diagram illustrating an example of anelectronic system in which a semiconductor device according to a fifthembodiment is used; and

FIG. 47 is an equivalent circuit diagram illustrating a module servingas the semiconductor device according to the fifth embodiment.

DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

In the embodiments described below, the invention will be described in aplurality of sections or embodiments when required as a matter ofconvenience. However, these sections or embodiments are not irrelevantto each other unless otherwise stated, and the one relates to the entireor a part of the other as a modification example, details, or asupplementary explanation thereof.

Also, in the embodiments described below, when referring to the numberof elements (including number of pieces, values, amount, range, andothers), the number of the elements is not limited to a specific numberunless otherwise stated or except the case where the number isapparently limited to a specific number in principle. The number largeror smaller than the specified number is also applicable.

Further, in the embodiments described below, it goes without saying thatthe components (including element steps) are not always indispensableunless otherwise stated or except the case where the components areapparently indispensable in principle. Similarly, in the embodimentsdescribed below, when the shape of the components, positional relationthereof, and others are mentioned, the substantially approximate andsimilar shapes and others are included therein unless otherwise statedor except the case where it is conceivable that they are apparentlyexcluded in principle. The same goes for the numerical value and therange described above.

Hereinafter, typical embodiments of the present invention will bedescribed based on the drawings. Note that components having the samefunction are denoted by the same reference symbols throughout all thedrawings for describing the embodiment, and the repetitive descriptionthereof will be omitted. Also, in the following embodiments, thedescription of the same or similar parts is not repeated in principleunless otherwise particularly required.

Further, in some drawings used in the embodiments, hatching is omittedin some cases even in a cross-sectional view so as to make the drawingseasy to see. Also, hatching is used in some cases even in a plan view soas to make the drawings easy to see.

First Embodiment

Hereinafter, a semiconductor device according to a first embodiment willbe described in detail with reference to the drawings. The semiconductordevice according to the present first embodiment is a semiconductordevice including an IGBT having an EGE-type (emitter-gate-emitter-type)active cell region. Note that a phrase in which “an IGBT has an EGE-typeactive cell region means that a trench electrode arranged at a centeramong three trench electrodes arranged in an active cell region to bespaced from each other is electrically connected to a gate electrodewhile each of two trench electrodes arranged on both ends iselectrically connected to an emitter electrode.

<Configuration of Semiconductor Device>

First, a configuration of a semiconductor chip as the semiconductordevice according to the first embodiment will be described.

FIG. 1 is a plan view of a semiconductor chip as the semiconductordevice according to the first embodiment. Each of FIGS. 2 and 3 is aplan view of a principal part of the semiconductor device according tothe first embodiment. FIG. 4 is a cross-sectional view of a principalpart of the semiconductor device according to the first embodiment. FIG.3 illustrates a region AR3 surrounded by a dashed-two dotted line inFIG. 2 to be enlarged. Also, FIG. 4 is a cross-sectional view takenalong a line A-A in FIGS. 2 and 3.

Note that FIG. 1 illustrates a transparent-view state obtained byremoving an insulating film FPF (see FIG. 4) in order to facilitateunderstanding, and illustrates outer circumferences of a cell formationregion AR1, an emitter pad EP, and a gate pad GP by dashed-two dottedlines. Also, FIG. 2 illustrates a transparent-view state obtained byremoving the insulating film FPF, a gate wiring GL, an emitter electrodeEE, an interlayer insulating film IL, and a part of a p-type body regionPB (see FIG. 4) formed in an inactive cell region LCi in order tofacilitate understanding, and illustrates outer circumferences of thecell formation region AR1 and the gate wiring GL by dashed-two dottedlines.

As illustrated in FIG. 1, a semiconductor chip CHP as the semiconductordevice according to the present first embodiment includes asemiconductor substrate SS. The semiconductor substrate SS includes anupper surface Sa (see FIG. 4) serving as one main surface and a lowersurface Sb (see FIG. 4) serving as the other main surface on an oppositeside of the upper surface. The semiconductor substrate SS also includesthe cell formation region AR1 serving as a partial region of the uppersurface Sa and a gate wiring extraction region AR2 serving as anotherpartial region of the upper surface Sa. The gate wiring extractionregion AR2 is provided, for example, on an outer circumferential side ofthe semiconductor substrate SS with reference to the cell formationregion AR1.

The emitter electrode EE is provided in the cell formation region AR1. Acenter part of the emitter electrode EE is the emitter pad EP configuredto connect a bonding wire or others. The emitter pad EP is a part of theemitter electrode EE exposed from an opening portion OP1 formed in theinsulating film FPF (see FIG. 4) formed to cover the emitter electrodeEE. The emitter electrode EE is made of a metal film containing, forexample, aluminum as a primarily component.

A gate wiring GL and a gate electrode GE are provided in the gate wiringextraction region AR2. The gate wiring GL is provided, for example, onthe outer circumferential side of the semiconductor substrate SS withreference to the emitter electrode EE. The gate wiring GL is connectedto the gate electrode GE. A center part of the gate electrode GE is thegate pad GP configured to connect a bonding wire or others. The gate padGP is a part of the gate electrode GE exposed from an opening portionOP2 formed in the insulating film FPF (see FIG. 4) formed to cover thegate electrode GE. The gate wiring GL and the gate electrode GE are madeof a metal film containing, for example, aluminum as a primarilycomponent.

As illustrated in FIGS. 1 to 4, two directions intersecting with,preferably, orthogonal to each other in the upper surface Sa of thesemiconductor substrate SS are set to an X axial direction and a Y axialdirection, and a direction perpendicular to the upper surface Sa of thesemiconductor substrate SS, that is, an up-down direction, is set to a Zaxial direction. At this time, in the cell formation region AR1, aplurality of hybrid cell regions LCh serving as active cell regions anda plurality of inactive cell regions LCi are provided as illustrated inFIG. 2. Each of the plurality of hybrid cell regions LCh extends in theY axial direction, and is periodically arranged in the X axial directionwhen seen in a plan view. Each of the plurality of inactive cell regionsLCi extends in the Y axial direction, and is periodically arranged inthe X axial direction when seen in a plan view. Also, the hybrid cellregion LCh and the inactive cell region LCi are arranged alternately inthe X axial direction.

In the present specification, note that a phrase “when seen in a planview” means a case of view from a direction perpendicular to the uppersurface Sa of the semiconductor substrate SS.

An element portion PR1 serving as a transistor of the IGBT is formed inthe hybrid cell region LCh, and an interposition portion PR2 interposedbetween the two element portions PR1 adjacent to each other is formed inthe inactive cell region LCi.

In the present specification, note that the explanation is made so thatthe respective components formed in the two respective hybrid cellregions LCh adjacent to each other are arranged to be symmetrical toeach other across the inactive cell region LCi located between the twohybrid cell regions LCh for convenience of the explanation. That is, theexplanation is made so that the respective components included in thetwo respective element portions PR1 adjacent to each other are arrangedto be symmetrical to each other across the interposition portion PR2interposed between the two element portions PR1. However, the respectivecomponents included in the two respective hybrid cell regions LChadjacent to each other may not be arranged to be symmetrical to eachother across the inactive cell region LCi located to be interposedbetween the two hybrid cell regions LCh. That is, the respectivecomponents included in the two respective element portions PR1 adjacentto each other may not be arranged to be symmetrical to each other acrossthe interposition portion PR2 interposed between the two elementportions PR1.

The hybrid cell region LCh includes a hybrid sub-cell region LCh1 and ahybrid sub-cell region LCh2. Also, in the hybrid cell region LCh, atrench electrode TG1 serving as a trench gate electrode is provided on aboundary surface between the hybrid sub-cell region LCh1 and the hybridsub-cell region LCh2.

The trench electrode TG1 is provided at a center of the hybrid cellregion LCh. This enables a width Wh1 of the hybrid sub-cell region LCh1and a width Wh2 of the hybrid sub-cell region LCh2 to be equal to eachother and enables the hybrid sub-cell region LCh1 and the hybridsub-cell region LCh2 to be symmetrical to each other across the trenchelectrode TG1.

In the hybrid cell region LCh, a trench electrode TG2 and a trenchelectrode TG3 are provided. The trench electrode TG2 and the trenchelectrode TG3 are provided on both sides in the X axial direction so asto interpose the trench electrode TG1 therebetween. The trench electrodeTG2 and the trench electrode TG3 are electrically connected to theemitter electrode EE.

In the hybrid sub-cell region LCh1, a plurality of n⁺-type emitterregions NE are provided in a part of the p-type body region PB on theupper surface Sa side of the semiconductor substrate SS. The p-type bodyregion PB is a p-conductivity type semiconductor region, and the n⁺-typeemitter region NE is an n-conductivity type semiconductor region whoseconductivity type is different from the p-conductivity type. In thehybrid sub-cell region LCh1, the p-type body region PB is formedcontinuously along the Y axial direction when seen in a plan view. Inthe hybrid sub-cell region LCh1, the plurality of n⁺-type emitterregions NE are arranged to be spaced from each other along the Y axialdirection.

In the present specification, note that the p-conductivity typesemiconductor may be a state in which only holes or both electrons andholes are charge carriers. However, it means that holes are main chargecarriers so that the concentration of holes is higher than theconcentration of electrons. Also, in the present specification, then-conductivity type semiconductor may be a state in which only electronsor both electrons and holes are charge carriers. However, it means thatelectrons are main charge carriers so that the concentration ofelectrons is higher than the concentration of holes.

In the hybrid sub-cell region LCh2, the plurality of n⁺-type emitterregions NE are provided in a part of the p-type body region PB on the supper surface Sa ide of the semiconductor substrate SS. In the hybridsub-cell region LCh2, the p-type body region PB is formed continuouslyalong the Y axial direction when seen in a plan view. In the hybridsub-cell region LCh2, the plurality of n⁺-type emitter regions NE arearranged to be spaced from each other along the Y axial direction.

In the inactive cell region LCi, two trench electrodes TG4 are provided.The two trench electrodes TG4 are provided to be spaced from each otherin the X axial direction. The two trench electrodes TG4 are electricallyconnected to the emitter electrode EE.

In the inactive cell region LCi, a p-type floating region PF is providedbetween the trench electrode TG3 and the trench electrode TG4 adjacentto each other. In the inactive cell region LCi, the p-type body regionPB is provided between the two trench electrodes TG4, but no p-typefloating region PF is provided between the two trench electrodes TG4.

Accordingly, as will be described below with reference to FIGS. 29, 30,and others, gate capacitance can be increased, and a rapid change oroscillation of current flowing in the IGBT at the time of turn-on can beprevented or suppressed. Also, this manner can enhance an IE effect canbe enhanced, and can decrease a switching loss of switching of the IGBT(hereinafter, referred to as “L load switching”) caused at the time ofturn-on when an inductor having an inductance L is connected as a loadto the collector electrode or the emitter electrode of the IGBT.

In the present specification, note that a switching operation in whichthe state of the IGBT is switched from an off state to an on state isreferred to as “turn-on” while a switching operation in which the stateof the IGBT is switched from an on state to an off state is referred toas “turn-off.”

Also, in the example illustrated in FIG. 2, the width Wh of the hybridcell region LCh in the X axial direction is shorter than a width Wi ofthe inactive cell region LCi in the X axial direction. In this case, theIE effect of the IGBT can be enhanced.

The gate wiring extraction region AR2 has a part provided with, forexample, a p-type floating region PFp, to surround the cell formationregion AR1. This p-type floating region PFp is electrically connected tothe emitter electrode EE via a part of a p⁺-type body contact regionPBCp exposed to a bottom surface of a contact trench CT.

The gate wiring GL is arranged in the gate wiring extraction region AR2,and the trench electrode TG1 extends from the inside of the cellformation region AR1 toward this gate wiring GL. In the gate wiringextraction region AR2, ends of the two adjacent trench electrodes TG1are connected to each other by a trench electrode TGz. The trenchelectrode TGz is arranged in a region in which the gate wiring GL isarranged when seen in a plan view. The trench electrode TGz iselectrically connected to the gate wiring GL via a connection electrodeGTG. Note that an end portion of the inactive cell region LCi on thegate wiring extraction region AR2 side is partitioned by an end portiontrench electrode TGp.

The two trench electrodes TG3 included in the two respective adjacenthybrid cell regions LCh are arranged on both sides across the inactivecell region LCi positioned between the two hybrid cell regions LCh.Also, the two trench electrodes TG4 are provided between the two trenchelectrodes TG3. The two trench electrodes TG3 and two trench electrodesTG4 are electrically connected by an emitter connection portion TGx madeof, for example, a poly-silicon film in addition to the end portiontrench electrode TGp. The emitter connection portion TGx is electricallyconnected to the emitter electrode EE via a connection electrode CTE. Bysuch a structure, reliability of electric connection between the emitterelectrode EE and the two trench electrodes TG3, two trench electrodesTG4, can be improved.

In the hybrid sub-cell region LCh1, a p⁺-type semiconductor region PRincluding a p⁺-type body contact region PBC and a p⁺-type latch-upprevention region PLP is formed. The p⁺-type semiconductor region PR isformed continuously along the Y axial direction. Also, in the hybridsub-cell region LCh1, the contact trench CT serving as an openingportion is formed continuously along the Y axial direction in the p-typebody region PB. The contact trench CT reaches the p⁺-type body contactregion PBC arranged in the hybrid sub-cell region LCh1.

Also, in the hybrid sub-cell region LCh2, the p⁺-type semiconductorregion PR including the p⁺-type body contact region PBC and the p⁺-typelatch-up prevention region PLP is formed. The p⁺-type semiconductorregion PR is formed continuously along the Y axial direction. Also, inthe hybrid sub-cell region LCh2, the contact trench CT serving as anopening portion is formed continuously along the Y axial direction inthe p-type body region PB. The contact trench CT reaches the p⁺-typebody contact region PBC arranged in the hybrid sub-cell region LCh2.

Next, configurations of the two element portions PR1 and theinterposition portion PR2 in the semiconductor device according to thefirst embodiment will be described, the two element portions PR1 beingprovided in the two adjacent hybrid cell regions LCh, respectively, andthe interposition portion PR2 being provided in the inactive cell regionLCi located between the two hybrid cell regions LCh and being interposedbetween the two element portions PR1. Specifically, a cross-sectionalstructure taken along a line A-A in FIGS. 2 and 3 will be described withreference to FIG. 4.

As illustrated in FIG. 4, the semiconductor substrate SS includes theupper surface Sa serving as a first main surface and the lower surfaceSb serving as a second main surface on the opposite side of the uppersurface Sa. An n-type semiconductor layer SLn is formed inside thesemiconductor substrate SS, and a semiconductor layer SLp is formedinside a part of the semiconductor substrate SS located on the lowersurface Sb side with reference to the semiconductor layer SLn.

An n⁻-type drift region ND serving as an n-type semiconductor region isformed in a part of the semiconductor layer SLn except for an upperlayer portion thereof. Between the semiconductor layer SLn and thesemiconductor layer SLp, an n-type field stop region Ns serving as ann-type semiconductor region is formed. Also, a p⁺-type collector regionCL serving as a p-type semiconductor region is formed of thesemiconductor layer SLp. Also, on the lower surface Sb of thesemiconductor substrate SS, a collector electrode CE electricallyconnected to the p⁺-type collector region CL, that is, the semiconductorlayer SLp, is formed. On the other hand, the p-type body region PB isprovided on the upper surface Sa side of the semiconductor substrate SS,that is, in the upper layer portion of the semiconductor layer SLn.

In the upper surface Sa of the semiconductor substrate SS, the elementportion PR1 is formed in the semiconductor layer SLn in each of the twohybrid cell regions LCh arranged to be spaced from each other in the Xaxial direction when seen in a plan view. In the upper surface Sa of thesemiconductor substrate SS, the interposition portion PR2 is formed inthe inactive cell region LCi located between the two hybrid cell regionsLCh when seen in a plan view, the interposition portion PR2 beinginterposed between the two element portions PR1 formed in the two hybridcell regions LCh, respectively. The gate electrode GE is electricallyconnected to the two element portions PR1, and the emitter electrode EEis electrically connected to the two element portions PR1.

Each of the two element portions PR1 formed in each of the two hybridcell regions LCh arranged to be spaced from each other in the X axialdirection includes trenches T1, T2, and T3, the trench electrodes TG1,TG2, and TG3, the two p-type body regions PB, and the plurality ofn⁺-type emitter regions NE.

As described above, each of the two hybrid cell regions LCh includes thehybrid sub-cell region LCh1 and the hybrid sub-cell region LCh2.

The trench T1 serving as a trench portion is formed on the upper surfaceSa side of the semiconductor substrate SS in a boundary portion betweenthe hybrid sub-cell region LCh1 and the hybrid sub-cell region LCh2. Thetrench T1 reaches the middle of the semiconductor layer SLn from theupper surface Sa, and extends in the Y axial direction when seen in aplan view.

On an inner wall of the trench T1, a gate insulating film GI is formed.In the trench T1, the trench electrode TG1 is formed on the gateinsulating film GI to fill the trench T1. That is, the trench electrodeTG1 included in each of the two element portions PR1 is buried insidethe trench T1 via the gate insulating film GI. The trench electrode TG1is electrically connected to the gate electrode GE (see FIG. 1). Notethat the trench electrode TG1 is formed continuously along the Y axialdirection when seen in a plan view.

In the hybrid sub-cell regions LCh1, the trench T2 serving as a trenchportion is formed on the upper surface Sa side of the semiconductorsubstrate SS. The trench T2 reaches the middle of the semiconductorlayer SLn from the upper surface Sa, extends in the Y axial directionwhen seen in a plan view, and is arranged on an opposite side of theinactive cell region LCi side located between the two hybrid cellregions LCh with reference to the trench T1.

On an inner wall of the trench T2, a gate insulating film GI is formed.In the trench T2, the trench electrode TG2 is formed on the gateinsulating film GI to fill the trench T2. That is, the trench electrodeTG2 is buried inside the trench T2 via the gate insulating film GI. Thetrench electrode TG2 is electrically connected to the emitter electrodeEE. That is, the trench electrode TG2 included in each of the twoelement portions PR1 is electrically connected to the emitter electrodeEE. Note that the trench electrode TG2 is formed continuously along theY axial direction when seen in a plan view.

In the hybrid sub-cell regions LCh2, the trench T3 serving as a trenchportion is formed on the upper surface Sa side of the semiconductorsubstrate SS. The trench T3 reaches the middle of the semiconductorlayer SLn from the upper surface Sa, extends in the Y axial directionwhen seen in a plan view, and is arranged on the inactive cell regionLCi side located between the two hybrid cell regions LCh with referenceto the trench T1.

On an inner wall of the trench T3, a gate insulating film GI is formed.In the trench T3, the trench electrode TG3 is formed on the gateinsulating film GI to fill the trench T3. That is, the trench electrodeTG3 is buried inside the trench T3 via the gate insulating film GI. Thetrench electrode TG3 is electrically connected to the emitter electrodeEE. That is, the trench electrode TG3 included in each of the twoelement portions PR1 is electrically connected to the emitter electrodeEE. Note that the trench electrode TG3 is formed continuously along theY axial direction when seen in a plan view.

In the hybrid sub-cell region LCh1, the p-type body region PB is formedin a part of the semiconductor layer SLn on the upper surface Sa side,the part being located between the trench T1 and the trench T2, andcontacts the gate insulating film GI formed on the inner wall of thetrench T1 and the gate insulating film GI formed on the inner wall ofthe trench T2. Also, in the hybrid sub-cell region LCh2, the p-type bodyregion PB is formed in a part of the semiconductor layer SLn on theupper surface Sa side, the part being located between the trench T1 andthe trench T3, and contacts the gate insulating film GI formed on theinner wall of the trench T1 and the gate insulating film GI formed onthe inner wall of the trench T3.

As illustrated in FIG. 4, in each of the hybrid sub-cell regions LCh1and LCh2 on a cross section taken along a line A-A in FIGS. 2 and 3, theplurality of n⁺-type emitter regions NE are formed only on the trenchelectrode TG1 side on the upper surface Sa side of the semiconductorsubstrate SS.

As described above, in the hybrid sub-cell region LCh1, the plurality ofn⁺-type emitter regions NE are arranged to be spaced from each otheralong the Y axial direction when seen in a plan view. In the hybridsub-cell region LCh2, the plurality of n⁺-type emitter regions NE arearranged to be spaced from each other along the Y axial direction whenseen in a plan view.

In the hybrid sub-cell region LCh1, each of the plurality of n⁺-typeemitter regions NE is formed in a part of the semiconductor layer SLn onthe upper surface Sa side, the part being located between the trench T1and the trench T2, and contacts the p-type body region PB and the gateinsulating film GI formed on the inner wall of the trench T1. Also, inthe hybrid sub-cell region LCh2, each of the plurality of n⁺-typeemitter regions NE is formed in a part of the semiconductor layer SLn onthe upper surface Sa side, the part being located between the trench T1and the trench T3, and contacts the p-type body region PB and the gateinsulating film GI formed on the inner wall of the trench T1.

The plurality of n⁺-type emitter regions NE formed in the hybridsub-cell region LCh1 are electrically connected to the emitter electrodeEE, and the plurality of n⁺-type emitter regions NE formed in the hybridsub-cell region LCh2 are electrically connected to the emitter electrodeEE. That is, the plurality of n⁺-type emitter regions NE each includedin the two element portions PR1 are electrically connected to theemitter electrode EE.

Preferably, in the hybrid sub-cell region LCh1, an n-type hole barrierregion NHB serving as an n-type semiconductor region is formed in a partof the semiconductor layer SLn, the part being located between thetrench T1 and the trench T2 and being located on the lower surface Sbside with reference to the p-type body region PB. Also, in the hybridsub-cell region LCh2, the n-type hole barrier region NHB serving as ann-type semiconductor region is formed in a part of the semiconductorlayer SLn, the part being located between the trench T1 and the trenchT3 and being located on the lower surface Sb side with reference to thep-type body region PB. That is, each of the two element portions PR1includes the two n-type hole barrier regions NHB.

In the hybrid sub-cell region LCh1, the n-type impurity concentration inthe n-type hole barrier region NHB is higher than the n-type impurityconcentration in a part (n⁻-type drift region ND) of the semiconductorlayer SLn, the part being located on the lower surface Sb side withreference to the n-type hole barrier region NHB. Also, in the hybridsub-cell region LCh2, the n-type impurity concentration in the n-typehole barrier region NHB is higher than the n-type impurity concentrationin a part (n⁻-type drift region ND) of the semiconductor layer SLn, thepart being located on the lower surface Sb side with reference to then-type hole barrier region NHB.

On the other hand, in the hybrid sub-cell region LCh1, the n-typeimpurity concentration in the n-type hole barrier region NHB is lowerthan the n-type impurity concentration in the n⁺-type emitter region NE.Also, in the hybrid sub-cell region LCh2, the n-type impurityconcentration in the n-type hole barrier region NHB is lower than then-type impurity concentration in the n⁺-type emitter region NE.

In the hybrid sub-cell region LCh1, note that the n-type hole barrierregion NHB may contact the p-type body region PB, the gate insulatingfilm GI formed on the inner wall of the trench T1, and the gateinsulating film GI formed on the inner wall of the trench T2. Also, inthe hybrid sub-cell region LCh2, the n-type hole barrier region NHB maycontact the p-type body region PB, the gate insulating film GI formed onthe inner wall of the trench T1, and the gate insulating film GI formedon the inner wall of the trench T3. This manner makes difficult todischarge the holes accumulated in the n⁻-type drift region ND to theemitter electrode EE in the hybrid sub-cell regions LCh1 and LCh2, andtherefore, the IE effect can be enhanced.

The interposition portion PR2 formed in the inactive cell region LCi andinterposed between the two adjacent element portions PR1 includes twotrenches T4, the two trench electrodes TG4, a p-type body region PB1serving as the p-type body region PB, and two p-type floating regionsPF1 serving as the p-type floating regions PF.

The two trenches 14 serving as trench portions are formed on the uppersurface Sa side of the semiconductor substrate SS in the inactive cellregion LCi. The two trenches 14 reach the middle of the semiconductorlayer SLn from the upper surface Sa of the semiconductor substrate SS,extends in the Y axial direction when seen in a plan view, and arearranged to be spaced from each other in the X axial direction.

On each of inner walls of the two trenches 14, the gate insulating filmGI is formed. In each of the two trenches 14, the trench electrode TG4is formed on the gate insulating film GI to fill the trench 14. That is,each of the two trench electrodes TG4 is buried in each of the trenches14 via the gate insulating film GI. The two trench electrodes TG4 areelectrically connected to the emitter electrode EE. That is, the twotrench electrodes TG4 included in the interposition portion PR2 areelectrically connected to the emitter electrode EE. Note that each ofthe two trench electrodes TG4 is formed continuously along the Y axialdirection when seen in a plan view.

In the inactive cell region LCi, the p-type body region PB is formed ina part of the semiconductor layer SLn on the upper surface Sa side, thepart being located between the trench T3 and the trench 14 adjacent toeach other. The p-type body region PB contacts the gate insulating filmGI formed on the inner wall of the trench T3 and the gate insulatingfilm GI formed on the inner wall of the trench T4 adjacent to the trenchT3.

In the inactive cell region LCi, the p-type floating region PF1 servingas the p-type floating region PF which is a p-type semiconductor regionis formed in a part of the semiconductor layer SLn, the part beinglocated between the trench T3 and the trench 14 adjacent to each otherand being located below the p-type body region PB.

Here, an object for providing the p-type floating region PF will bedescribed.

A saturation voltage of a voltage VCE in a forward direction serving asa voltage between the collector and the emitter is referred to asvoltage VCE (sat). At this time, in order to decrease the voltage VCE(sat), it is required to enhance the IE effect. On the other hand, whena load is short-circuited by an error operation or others in an inverterdescribed below with reference to FIG. 46, a large voltage is applied tothe IGBT, or a large short-circuit current flows in the IGBT. Therefore,the IGBT is required not to be broken until a protection circuit blocks.Here, when the short-circuit current flows in the IGBT because of theshort-circuited state of the load, a period of time taken when the IGBTcan be endured without being broken is called short circuit capacity.

In order to improve the short circuit capacity, it is required todecrease energy to be applied to the IGBT, that is, decrease thesaturation current flowing in the IGBT. In order to decrease thesaturation current, it is required to decrease an area of the n⁺-typeemitter region NE. And, in order to decrease the area of the n⁺-typeemitter region NE, two methods are considered.

A first method is to eliminate some of the n⁺-type emitter regions NE inthe Y axial direction. However, this method increases the voltage VCE(sat).

A second method is a method in the present first embodiment, and is amethod of eliminating some of the n⁺-type emitter regions NE in the Xaxial direction by providing the p-type floating region PF in theinactive cell region LCi. In this manner, a discharge path for the holeswhich are the carriers is narrowed, so that the IE effect is enhanced.That is, the p-type floating region PF is for improving the shortcircuit capacity by eliminating some of the n⁺-type emitter regions NEin the X axial direction.

Also, in the inactive cell region LCi, the p-type body region PB1serving as the p-type body region PB is provided in a part of thesemiconductor layer SLn on the upper surface Sa side, the part beinglocated between the two trenches T4. However, in the inactive cellregion LCi, the p-type floating region PF is not formed in a part of thesemiconductor layer SLn, the part being located between the two trenchesT4 and being located below the p-type body region PB.

That is, the interposition portion PR2 provided in the inactive cellregion LCi includes the p-type body region PB1 formed in the part of thesemiconductor layer SLn, the part being located between the two trenchesT4. In the inactive cell region LCi, the interposition portion PR2 alsoincludes the two p-type floating regions PF1 formed in two parts of thesemiconductor layer SLn, the parts being located on both sides of thep-type body region PB1 in the X axial direction via the two respectivetrenches T4.

Each of two parts of the inactive cell region LCi is referred to as apart LCi1, the part being located between the adjacent trench T3 andtrench T4. Also, a part of the inactive cell region LCi is referred toas a part LCi2, the part being located between the two trenches T4.

At this time, in the inactive cell region LCi, an end portion (lowerend), on the lower surface Sb side, of each of the two p-type floatingregions PF1 formed in the two respective parts LCi1 is arranged on thelower surface Sb side (lower side) in the Z axial direction withreference to an end portion (lower end), on the lower surface Sb side,of the p-type body region PB1 formed in the part LCi2. In other words,the lower end of each of the two p-type floating regions PF1 is arrangedto be lower in the Z axial direction than the lower end of the p-typebody region PB1. In the inactive cell region LCi, an n⁻-type driftregion ND is formed in a part of the semiconductor layer SLn, the partbeing located between the two trenches T4 and being located below thep-type body region PB1.

That is, in the present first embodiment, in the inactive cell regionLCi located between the two adjacent hybrid cell regions LCh, the p-typefloating region PF is divided into two by the two trenches T4.

Accordingly, as described below with reference to FIGS. 29, 30 andothers, the gate capacitance can be increased, and the rapid change oroscillation of current flowing in the IGBT at the time of turn-on can beprevented or suppressed. Also, the IE effect can be enhanced, and theswitching loss at the time of turn-on of the load L switching can bedecreased.

Preferably, in each of the two parts LCi1 in the inactive cell regionLCi, the end portion of the p-type floating region PF1 on the lowersurface Sb side is arranged on the lower surface Sb side in the Z axialdirection with reference to an end portion of the trench T3 on the lowersurface Sb side. That is, the end portion of the p-type floating regionPF1 on the lower surface Sb side is arranged on the lower surface Sbside in the Z axial direction with reference to the end portion of thetrench T3 on the lower surface Sb side, the trench T3 being adjacent tothe trench T4 via the p-type floating region PF1. In other words, in aset of the trench T3 and the p-type floating region PF1 adjacent to eachother, the end portion of the p-type floating region PF on the lowersurface Sb side is arranged on the lower surface Sb side in the Z axialdirection with reference to the end portion of the trench T3 on thelower surface Sb side. Accordingly, an electric field can be preventedor suppressed from focusing on a part of the semiconductor layer SLn,the part being located in vicinity of the end portion of the trench T3on the lower surface Sb side, and a breakdown voltage of the IGBT can beimproved.

In each of the two parts LCi1 in the inactive cell region LCi, thep-type floating region PF may contact the gate insulating film GI formedon the inner wall of the trench T3. Also, in each of the two parts LCi1in the inactive cell region LCi, the p-type floating region PF maycontact the gate insulating film GI formed on the inner wall of thetrench 14.

As illustrated in FIG. 4, in the hybrid cell regions LCh and theinactive cell regions LCi, the interlayer insulating film IL, made of,for example, silicon oxide, is formed on the upper surface Sa of thesemiconductor substrate SS. In each of the hybrid sub-cell regions LCh1and LCh2 and the inactive cell regions LCi, the interlayer insulatingfilm IL is formed to cover the p-type body region PB. Note that aninsulating film IF may be formed between the upper surface Sa of thesemiconductor substrate SS and the interlayer insulating film IL.

In each of the hybrid sub-cell regions LCh1 and LCh2 in the presentfirst embodiment, the interlayer insulating film IL and thesemiconductor layer SLn have the contact trench CT formed as an openingportion which penetrates the interlayer insulating film IL and whichreaches the middle of the semiconductor layer SLn. In each of the hybridsub-cell regions LCh1 and LCh2, the contact trench CT is formedcontinuously along the Y axial direction when seen in a plan view.

In each of the hybrid sub-cell regions LCh1 and LCh2, the p⁺-type bodycontact region PBC serving as a p-type semiconductor region is formed ina part of the p-type body region PB, the part being exposed to a bottomsurface of the contact trench CT. Also, below the p⁺-type body contactregion PBC, the p⁺-type latch-up prevention region PLP serving as ap-type semiconductor region is formed. The p⁺-type semiconductor regionPR is formed of the p⁺-type body contact region PBC and the p⁺-typelatch-up prevention region PLP.

That is, in each of the hybrid sub-cell regions LCh1 and LCh2, thep⁺-type semiconductor region PR includes the p⁺-type body contact regionPBC and the p⁺-type latch-up prevention region PLP. In each of thehybrid sub-cell regions LCh1 and LCh2, the p-type impurity concentrationin the p⁺-type body contact region PBC is higher than the p-typeimpurity concentration in the p⁺-type latch-up prevention region PLP.Also, in each of the hybrid sub-cell regions LCh1 and LCh2, the p-typeimpurity concentration in the p⁺-type latch-up prevention region PLP ishigher than the p-type impurity concentration in the p-type body region.That is, in each of the hybrid sub-cell regions LCh1 and LCh2, thep-type impurity concentration in the p⁺-type semiconductor region PR ishigher than the p-type impurity concentration in the p-type body region.

In each of the hybrid sub-cell regions LCh1 and LCh2, the p⁺-typesemiconductor region PR is formed in a part of the p-type body regionPB, the part being exposed to the contact trench CT. In the hybridsub-cell region LCh1, the p⁺-type semiconductor region PR is formed in apart of the semiconductor layer SLn, the part being located between thetrench T1 and the trench T2. Also, in the hybrid sub-cell region LCh2,the p⁺-type semiconductor region PR is formed in a part of thesemiconductor layer SLn, the part being located between the trench T1and the trench T3.

In the hybrid sub-cell region LCh1, a connection electrode CP buried inthe contact trench CT is formed. Also, in the hybrid sub-cell regionLCh2, the connection electrode CP buried in the contact trench CT isformed. That is, each of the two element portions PR1 includes theinterlayer insulating film IL, the two contact trenches CT, the twop⁺-type semiconductor regions PR, and the two connection electrodes CP.

In each of the hybrid sub-cell regions LCh1 and LCh2, the connectionelectrode CP contacts the n⁺-type emitter region NE and the p⁺-typesemiconductor region PR. Thus, in each of the hybrid sub-cell regionsLCh1 and LCh2, the n⁺-type emitter region NE and the p⁺-typesemiconductor region PR are electrically connected to the emitterelectrode EE via the connection electrode CP. That is, the p-type bodyregion PB included in each of the two element portions PR1 iselectrically connected to the emitter electrode EE.

In a set of the connection electrode CP and the p⁺-type semiconductorregion PR connected to each other in each of the hybrid sub-cell regionsLCh1 and LCh2, the connection electrode CP contacts the p⁺-type bodycontact region PBC included in the p⁺-type semiconductor region PR.Accordingly, a contact resistance between the connection electrode CPand the p⁺-type semiconductor region PR can be decreased.

As illustrated in FIG. 4, the emitter electrode EE formed of a metalfilm mainly containing, for example, aluminum as a main component isprovided on the interlayer insulating film IL, and the emitter electrodeEE is connected to the n⁺-type emitter region NE and the p⁺-type bodycontact region PBC via the connection electrode CP formed in the contacttrench CT. In the example illustrated in FIG. 4, the connectionelectrode CP and the emitter electrode EE are formed integrally.

On the emitter electrode EE, the insulating film FPF serving as apassivation film made of, for example, a polyimide-based organicinsulating film or others is further formed.

In the hybrid cell region LCh, the IGBT is formed of the collectorelectrode CE, the p⁺-type collector region CL, the n⁻-type drift regionND, the p-type body region PB, the p⁺-type semiconductor region PR, then⁺-type emitter region NE, the trench electrode TG1, and the gateinsulating film GI formed on the inner wall of the trench T1.

<Method of Manufacturing Semiconductor Device>

Next, a method of manufacturing the semiconductor device according tothe first embodiment will be described. Each of FIGS. 5 to 20 is across-sectional view of a principal part illustrating a step ofmanufacturing the semiconductor device according to the firstembodiment. Each of FIGS. 5 to 20 is a cross-sectional view taken alonga line A-A in FIG. 3 as similar to FIG. 4.

Hereinafter, the cell formation region AR1 (see FIG. 2) will be mainlydescribed, and the gate wiring extraction region AR2 (see FIG. 2) willbe described with reference to FIG. 2 as needed. Also, hereinafter,description will be made about a case in which the two element portionsPR1 are provided in the two adjacent hybrid cell regions LCh,respectively, and in which the interposition portion PR2 interposedbetween the two element portions PR1 is formed in the inactive cellregion LCi located between the two hybrid cell regions LCh.

Note that each of the two adjacent hybrid cell regions LCh includes thehybrid sub-cell regions LCh1 and LCh2. Also, the inactive cell regionLCi located between the two hybrid cell regions LCh includes two partsLCi1 each located between the trench T3 (see FIG. 9) and the trench 14(see FIG. 9) adjacent to each other and one part LCi2 located betweenthe two trenches 14.

First, as illustrated in FIG. 5, the semiconductor substrate SS made ofa silicon single crystal into which an n-type impurity such asphosphorus (P) has been doped is prepared. The semiconductor substrateSS includes the upper surface Sa serving as a first main surface and thelower surface Sb serving as a second main surface on the opposite sideof the upper surface Sa.

The impurity concentration of the n-type impurity in the semiconductorsubstrate SS can be set to, for example, about 2×10¹⁴ cm⁻³. Thesemiconductor substrate SS is a flattened substantially circularsemiconductor thin plate called a wafer at this stage. A thickness ofthe semiconductor substrate SS can be set to, for example, about 450 μmto 1000 μm.

Note that a semiconductor layer of the semiconductor substrate SS is setto the semiconductor layer SLn, the semiconductor layer being on theupper surface Sa side with reference to a semiconductor layer providedwith the n-type field stop region Ns (see FIG. 4). The semiconductorlayer SLn is an n-type semiconductor layer. Therefore, when thesemiconductor substrate SS is prepared, the n-type semiconductor layerSLn is formed inside the semiconductor substrate SS.

Next, a resist film R1 for introducing the n-type hole barrier region isformed on the entire upper surface Sa of the semiconductor substrate SSby coating or others, and is patterned by normal lithography. Whileusing the patterned resist film R1 as a mask, an n-type impurity isdoped into the upper surface Sa of the semiconductor substrate SS by,for example, ion implantation, so that the n-type hole barrier regionNHB is formed. As for the ion implantation conditions at this time, ionimplantation conditions in which an ion species is phosphorus (P), inwhich the dose amount is about 6×10¹² cm⁻², and in which implantationenergy is about 80 keV can be exemplified as preferable conditions.Then, an unnecessary resist film R1 is removed by asking or others.

Note that the n-type hole barrier region NHB is formed in each of thehybrid sub-cell regions LCh1 and LCh2 included in each of the twoadjacent hybrid cell regions LCh.

Next, as illustrated in FIG. 6, a resist film R2 for introducing thep-type floating region is formed on the upper surface Sa of thesemiconductor substrate SS by coating or others, and is patterned bynormal lithography. While using the patterned resist film R2 as a mask,a p-type impurity is doped into the upper surface Sa of thesemiconductor substrate SS by, for example, ion implantation, so thatthe p-type floating region PF is formed. As for the ion implantationconditions at this time, ion implantation conditions in which an ionspecies is boron (B), in which the dose amount is about 3.5×10¹³ cm⁻²,and in which implantation energy is about 75 keV can be exemplified aspreferable conditions. Then, an unnecessary resist film R2 is removed byashing or others.

Note that the p-type floating region PF is formed in each of the twoparts LCi1 included in the inactive cell region LCi. Also, when thep-type floating region PF is formed in the cell formation region AR1(see FIG. 2), the p-type floating region PFp is formed in, for example,the gate wiring extraction region AR2 (see FIG. 2).

Next, as illustrated in FIG. 7, a hard mask film HM made of, forexample, silicon oxide, is formed on the upper surface Sa of thesemiconductor substrate SS by, for example, a CVD (chemical vapordeposition) method or others. A thickness of the hard mask film HM is,for example, about 450 nm.

Next, as illustrated in FIG. 7, a resist film R3 for processing the hardmask film is formed on the upper surface Sa of the semiconductorsubstrate SS by coating or others, and is patterned by normallithography. While using the patterned resist film R3 as a mask, thehard mask film HM is patterned by, for example, dry etching.

Then, as illustrated in FIG. 8, the unnecessary resist film R3 isremoved by ashing or others.

Next, as illustrated in FIG. 9, the trenches T1, T2, T3, and T4 areformed by, for example, anisotropic dry etching while using thepatterned hard mask film HM. As for gas for this anisotropic dryetching, for example, Cl₂/O₂-based gas can be exemplified as apreferable gas.

At this time, in each of the two adjacent hybrid cell regions LCh, thetrench T1 which reaches the middle of the semiconductor layer SLn fromthe upper surface Sa of the semiconductor substrate SS and which extendsin the Y axial direction when seen in a plan view is formed. Also, ineach of the two hybrid cell regions LCh, the trench T2 which reaches themiddle of the semiconductor layer SLn from the upper surface Sa of thesemiconductor substrate SS, which extends in the Y axial direction whenseen in a plan view, and which is arranged on the side the opposite sideof the inactive cell region LCi side located between the two hybrid cellregions LCh with respect to the trench T1 is formed. Also, in each ofthe two hybrid cell regions LCh, the trench T3 which reaches the middleof the semiconductor layer SLn from the upper surface Sa of thesemiconductor substrate SS, which extends in the Y axial direction whenseen in a plan view, and which is arranged on the inactive cell regionLCi side located between the two hybrid cell regions LCh with respect tothe trench T1 is formed.

Meanwhile, in the inactive cell region LCi, the two trenches 14 each ofwhich reaches the middle of the semiconductor layer SLn from the uppersurface Sa of the semiconductor substrate SS, each of which extends inthe Y axial direction when seen in a plan view, and each of which isarranged to be spaced from each other in the X axial direction areformed.

Then, as illustrated in FIG. 10, the unnecessary hard mask film HM isremoved by wet etching using, for example, a hydrofluoric-acid-basedetchant.

Next, as illustrated in FIG. 11, drive-in diffusion (for example, at1200° C. for about 30 minutes) for the p-type floating regions PF andthe n-type hole barrier regions NHB is performed. At this time, thedrive-in diffusion is performed so that the end portion of the p-typefloating region PF on the lower surface Sb side is arranged on the lowersurface Sb side in the Z axial direction with reference to the endportion of the p-type body region PB on the lower surface Sb side, thep-type body region PB being formed in a step described below withreference to FIG. 15.

Preferably, the drive-in diffusion is performed so that the end portionof the p-type floating region PF on the lower surface Sb side isarranged on the lower surface Sb side in the Z axial direction withreference to all of the end portion of the trench T1 on the lowersurface Sb side, the end portion of the trench T2 on the lower surfaceSb side, the end portion of the trench T3 on the lower surface Sb side,and the end portion of the trench 14 on the lower surface Sb side.

Thus, in each of the two parts LCi1, the p-type floating region PF1serving as the p-type floating region PF is formed in a part of thesemiconductor layer SLn, the part being located between the trench T3and the trench 14 adjacent to each other. On the other hand, the p-typefloating region PF is not formed in a part of the semiconductor layerSLn, the part being located between the two trenches 14.

Preferably, the p-type floating region PF1 formed in each of the twoparts LCi1 contacts the gate insulating film GI formed on the inner wallof the trench T3.

Also, the n-type hole barrier regions NHB are formed in parts of thesemiconductor layer SLn, the parts being located between the trench T1and the trench T2 and between the trench T1 and the trench T3.Preferably, the n-type hole barrier region NHB formed between the trenchT1 and the trench T2 contacts the gate insulating film GI formed on theinner wall of the trench T1 and the gate insulating film GI formed onthe inner wall of the trench T2. Also, preferably, the n-type holebarrier region NHB formed between the trench T1 and the trench T3contacts the gate insulating film GI formed on the inner wall of thetrench T1 and the gate insulating film GI formed on the inner wall ofthe trench T3.

Also, in the drive-in diffusion, a region of the n-type semiconductorsubstrate SS, the region not having the p-type floating region PF andthe n-type hole barrier region NHB, becomes the n⁻-type drift region ND.

Specifically, in each of the hybrid sub-cell regions LCh1 and LCh2included in the hybrid cell region LCh, a region of the n-typesemiconductor layer SLn, the region not having the p-type floatingregion PF and the n-type hole barrier region NHB, becomes the n⁻-typedrift region ND.

On the other hand, in the part LCi1 included in the inactive cell regionLCi, a region of the n-type semiconductor layer SLn, the region nothaving the p-type floating region PF, becomes the n⁻-type drift regionND. Also, in the part LCi2 included in the inactive cell region LCi, theentirety including a part of the semiconductor layer SLn, the part beinglocated between the two trenches T4, becomes the n⁻-type drift regionND.

In the step illustrated in FIG. 11, note that the n⁻-type drift regionND is formed in a region from the inside of the semiconductor layer SLnto the lower surface Sb of the semiconductor substrate SS.

In the hybrid sub-cell region LCh1, the n-type impurity concentration inthe n-type hole barrier region NHB formed between the trench T1 and thetrench T2 is higher than the n-type impurity concentration in a part ofthe semiconductor layer SLn, the part being located on the lower surfaceSb side with reference to the n-type hole barrier region NHB, that is,in the n⁻-type drift region ND. Also, in the hybrid sub-cell regionLCh1, the n-type impurity concentration in the n-type hole barrierregion NHB formed between the trench T1 and the trench T2 is lower thanthe n-type impurity concentration in the n⁺-type emitter region NE (seeFIG. 15 described below).

In the hybrid sub-cell region LCh2, the n-type impurity concentration inthe n-type hole barrier region NHB formed between the trench T1 and thetrench T3 is higher than the n-type impurity concentration in a part ofthe semiconductor layer SLn, the part being located on the lower surfaceSb side with reference to the n-type hole barrier region NHB, that is,in the n⁻-type drift region ND. Also, in the hybrid sub-cell regionLCh2, the n-type impurity concentration in the n-type hole barrierregion NHB formed between the trench T1 and the trench T3 is lower thanthe n-type impurity concentration in the n⁺-type emitter region NE (seeFIG. 15 described below).

Next, as illustrated in FIG. 11, the gate insulating film GI made of,for example, silicon oxide is formed on the upper surface Sa of thesemiconductor substrate SS and on each inner wall of the trenches T1,T2, T3, and T4 by, for example, a thermal oxidation method or others. Athickness of the gate insulating film GI is, for example, about 0.12 μm.

Next, as illustrated in FIG. 12, a conductive film CF made of, forexample, phosphorus (P)-doped poly-silicon is formed on the uppersurface Sa of the semiconductor substrate SS and each inside of thetrenches T1, T2, T3, and T4 by, for example, a CVD method or others. Athickness of the conductive film CF is, for example, about 0.6 μm.

Next, as illustrated in FIG. 13, the conductive film CF is etched backby, for example, dry etching or others. Thus, the trench electrode TG1made of the conductive film CF buried inside the trench T1 via the gateinsulating film GI is formed. Also, the trench electrode TG2 made of theconductive film CF buried inside the trench T2 via the gate insulatingfilm GI is formed, and the trench electrode TG3 made of the conductivefilm CF buried inside the trench T3 via the gate insulating film GI isformed. Also, the two trench electrodes TG4 made of the conductive filmsCF buried inside the two respective trenches T4 via the gate insulatingfilm GI are formed. As for gas for this etching, for example, SF₆ gascan be exemplified as a preferable gas.

Next, as illustrated in FIG. 14, the gate insulating film GI except foreach inside of the trenches T1, T2, T3, and T4 is removed by dry etchingor others.

Next, as illustrated in FIG. 15, the insulating film IF made of arelatively thin silicon oxide film (as thin as, for example, the gateinsulating film GI) for ion implantation performed later is formed onthe upper surface Sa of the semiconductor substrate SS by, for example,a thermal oxidation method or a CVD method. Next, a resist film(illustration is omitted) for introducing the p-type body region isformed on the upper surface Sa of the semiconductor substrate SS bynormal lithography. While using this resist film for introducing thep-type body region as a mask, a p-type impurity is doped into the entirecell formation region AR1 (see FIG. 2) and other necessary parts by, forexample, ion implantation, so that the p-type body region PB is formed.

Specifically, in the hybrid sub-cell region LCh1, the p-type body regionPB is formed in a part of the semiconductor layer SLn on the uppersurface Sa side, the part being located between the trench T1 and thetrench T2, so as to contact the gate insulating film GI formed on theinner wall of the trench T1 and the gate insulating film GI formed onthe inner wall of the trench T2. At this time, in the hybrid sub-cellregion LCh1, the n-type hole barrier region NHB is formed in a part ofthe semiconductor layer SLn, the part being located between the trenchT1 and the trench T2 and being located on the lower surface Sb side withreference to the p-type body region PB.

Also, in the hybrid sub-cell region LCh2, the p-type body region PB isformed in a part of the semiconductor layer SLn on the upper surface Saside, the part being located between the trench T1 and the trench T3, soas to contact the gate insulating film GI formed on the inner wall ofthe trench T1 and the gate insulating film GI formed on the inner wallof the trench T3. At this time, in the hybrid sub-cell region LCh2, then-type hole barrier region NHB is formed in a part of the semiconductorlayer SLn, the part being located between the trench T1 and the trenchT3 and being located on the lower surface Sb side with reference to thep-type body region PB.

On the other hand, in the part LCi2 included in the inactive cell regionLCi, the p-type body region PB1 serving as the p-type body region PB isformed in a part of the semiconductor layer SLn on the upper surface Saside, the part being located between the two trenches T4, so as tocontact the gate insulating film GI formed on each inner wall of the twotrenches 14.

At this time, the p-type body region PB1 is formed so that an endportion of the p-type floating region PF1 on the lower surface Sb side,the end portion being formed in the part LCi1 included in the inactivecell region LCi, is arranged on the lower surface Sb side in the Z axialdirection with reference to an end portion of the p-type body region PB1on the lower surface Sb side, the part being formed in the part LCi2included in the inactive cell region LCi.

Thus, in the parts LCi1 included in the inactive cell region LCi, thetwo p-type floating regions PF1 are formed in two parts of thesemiconductor layer SLn, the two part being located on both sides of thep-type body region PB1 in the X axial direction via the two respectivetrenches T4. On the other hand, in the part LCi2 included in theinactive cell region LCi, the n⁻-type drift region ND is formed in apartof the semiconductor layer SLn, the part being located between the twotrenches T4 and being located below the p-type body region PB.

In each of the two parts LCi1 of the inactive cell region LCi, note thatthe p-type body region PB may be formed in a part of the semiconductorlayer SLn on the upper surface Sa side, the part being located betweenthe trench T3 and the trench 14 adjacent to each other, so as to contactthe gate insulating film GI formed on the inner wall of the trench T3and the gate insulating film GI formed on the inner wall of the trench14.

As for ion implantation conditions at this time, ion implantationconditions in which an ion species is boron (B), in which the doseamount is about 3×10¹³ cm⁻², and in which implantation energy is about75 keV can be exemplified as preferable conditions. Then, theunnecessary resist film for introducing the p-type body region isremoved by asking or others.

When the p-type body region PB is formed in each of the hybrid sub-cellregions LCh1 and LCh2 in the step of manufacturing the semiconductordevice according to the present first embodiment, the p-type body regionPB1 is formed in the part LCi2 included in the inactive cell region LCi.Thus, in the step of manufacturing the semiconductor device according tothe present first embodiment, it is not required to prepare anadditional mask for forming the p-type body region PB1, and it is notrequired to perform additional lithography for forming the p-type bodyregion PB1.

Further, a resist film (illustration is omitted) for introducing then⁺-type emitter region is formed on the upper surface Sa of thesemiconductor substrate SS by normal lithography. While using thisresist film for introducing the n⁺-type emitter region as a mask, ann-type impurity is doped into the upper layer portion of the p-type bodyregion PB in the hybrid cell region LCh by, for example, ionimplantation, so that the n⁺-type emitter region NE is formed.

Specifically, in the hybrid sub-cell region LCh1, the n⁺-type emitterregion NE is formed in a part of the semiconductor layer SLn, the partbeing located between the trench T1 and the trench T2, so as to contactthe gate insulating film GI formed on the inner wall of the trench T1and the p-type body region PB. Also, in the hybrid sub-cell region LCh2,the n⁺-type emitter region NE is formed in a part of the semiconductorlayer SLn, the part being located between the trench T1 and the trenchT3 so as to contact the gate insulating film GI formed on the inner wallof the trench T1 and the p-type body region PB.

As for ion implantation conditions at this time, ion implantationconditions in which an ion species is arsenic (As), in which the doseamount is about 5×10¹⁵ cm⁻², and in which implantation energy is about80 keV can be exemplified as preferable conditions. The, the unnecessaryresist film for introducing the n⁺-type emitter region is removed byashing or others.

Next, as illustrated in FIG. 16, the interlayer insulating film IL madeof, for example, a PSG (phosphosilicate glass) film is formed on theupper surface Sa of the semiconductor substrate SS by, for example, aCVD method. The interlayer insulating film IL is formed to cover, forexample, the p-type body region PB via the insulating film IF in each ofthe hybrid sub-cell regions LCh1 and LCh2 and the inactive cell regionsLCi. A thickness of the interlayer insulating film IL is, for example,about 0.6 μm. As for a material for this interlayer insulating film IL,not only the PSG film but also a BPSG (boronphosphosilicate glass) film,an NSG (non-doped silicate glass) film, an SOG (spin-on-glass) film, anda composite film of them, can be exemplified as a preferable material.

Next, as illustrated in FIG. 17, a resist film (illustration is omitted)for forming the contact trench is formed on the interlayer insulatingfilm IL by normal lithography. Subsequently, the contact trench CT isformed by, for example, anisotropic dry etching or others. As for gasused for this anisotropic dry etching, for example, mixed gas containingAr gas, CHF₃ gas, and CF₄ gas or others can be exemplified as apreferable gas. Then, the unnecessary resist film for forming thecontact trench is removed by ashing or others.

Next, as illustrated in FIG. 17, the contact trench CT is extended intothe semiconductor substrate SS by, for example, anisotropic dry etching.As for gas for this anisotropic dry etching, for example, Cl₂/O₂ gas canbe exemplified as a preferable gas.

By a step illustrated in FIG. 17, the contact trench CT serving as anopening portion is formed in each of the hybrid sub-cell regions LCh1and LCh2 to penetrate the interlayer insulating film IL and reach themiddle of the p-type body region PB. In each of the hybrid sub-cellregions LCh1 and LCh2, the contact trench CT is formed continuouslyalong the Y axial direction when seen in a plan view.

Next, as illustrated in FIG. 18, the p⁺-type body contact region PBC isformed by, for example, ion-implanting a p-type impurity through thecontact trench CT. Here, as for ion implantation conditions, ionimplantation conditions in which an ion species is boron (B), in whichthe dose amount is about 5×10¹⁵ cm⁻², and in which implantation energyis about 80 keV can be exemplified as preferable conditions.

Similarly, the p⁺-type latch-up prevention region PLP is formed by, forexample, ion-implanting a p-type impurity through the contact trench CT.Here, as for ion implantation conditions, ion implantation conditions inwhich an ion species is boron (B), in which the dose amount is about5×10¹⁵ cm⁻², and in which implantation energy is about 80 keV can beexemplified as preferable conditions. The p-type impurity concentrationin the p⁺-type body contact region PBC is higher than the p-typeimpurity concentration in the p⁺-type latch-up prevention region PLP.Also, the p⁺-type semiconductor region PR is formed of the p⁺-type bodycontact region PBC and the p⁺-type latch-up prevention region PLP.

By a step illustrated in FIG. 18, the p⁺-type semiconductor region PR isformed in each of the hybrid sub-cell regions LCh1 and LCh2 in a part ofthe p-type body region PB, the part being exposed to the contact trenchCT. In each of the hybrid sub-cell regions LCh1 and LCh2, the p⁺-typesemiconductor region PR is formed continuously along the Y axialdirection when seen in a plan view.

That is, by the step illustrated in FIG. 18, the p⁺-type semiconductorregion PR contacting the p-type body region PB is formed in a part ofthe semiconductor layer SLn, the part being located between the trenchT1 and the trench T2. Also, the p⁺-type semiconductor region PRcontacting the p-type body region PB is formed in a part of thesemiconductor layer SLn, the part being located between the trench T1and the trench T3. In each of the hybrid sub-cell regions LCh1 and LCh2,the p-type impurity concentration in the p⁺-type semiconductor region PRis higher than the p-type impurity concentration in the p-type bodyregion PB.

Next, as illustrated in FIG. 19, the emitter electrode EE is formed.Specifically, the formation is performed in, for example, the followingprocedure. First, a TiW film is formed on the upper surface Sa of thesemiconductor substrate SS as a barrier metal film by, for example,sputtering. A thickness of the TiW film is, for example, about 0.2 μm.Titanium in the TiW film mostly moves to the silicon interface and formssilicide by a thermal treatment performed later, and contributes toimprovement of contact characteristics. However, these processes arecomplicated, and therefore, are not shown in the drawing.

Next, after silicide annealing is performed, for example, at about 600°C. for about 10 minutes under a nitrogen atmosphere, an aluminum-basedmetal film (in which, for example, several % of silicon is added, andthe rest is aluminum) is formed on the entire surface of the barriermetal film by, for example, sputtering to fill the contact trench CT. Athickness of the aluminum-based metal film is, for example, about 5 μm.

Next, a resist film (illustration is omitted) for forming the emitterelectrode is formed by normal lithography. Subsequently, the emitterelectrode EE made of the aluminum-based metal film and the barrier metalfilm is patterned by, for example, dry etching. As for gas for this dryetching, for example, Cl₂/BCl₃ gas can be exemplified as a preferablegas. Then, the unnecessary resist film for forming the emitter electrodeis removed by asking or others.

By a step illustrated in FIG. 19, the connection electrode CP buriedinside the contact trench CT and the emitter electrode EE formed on theinterlayer insulating film IL are formed in the hybrid sub-cell regionLCh1. In the hybrid sub-cell region LCh1, the connection electrode CP isformed continuously along the Y axial direction when seen in a planview. Also, by the step illustrated in FIG. 19, the connection electrodeCP buried inside the contact trench CT and the emitter electrode EEformed on the interlayer insulating film IL are formed in the hybridsub-cell region LCh2. In the hybrid sub-cell region LCh2, the connectionelectrode CP is formed continuously along the Y axial direction whenseen in a plan view.

The emitter electrode EE is electrically connected to the n⁺-typeemitter region NE and the p⁺-type semiconductor region PR formed in eachof the hybrid sub-cell regions LCh1 and LCh2 via the connectionelectrode CP formed in the hybrid sub-cell region. When the emitterelectrode EE is formed, note that the gate electrode GE (see FIG. 1)electrically connected to the trench electrode TG1 may be formed.

When the emitter electrode EE is formed in the cell formation region AR1(see FIG. 2), note that the gate wiring GL and the gate electrode GE(see FIG. 1) can be formed in the gate wiring extraction region AR2 (seeFIG. 2).

Next, as illustrated in FIG. 19, the insulating film FPF serving as apassivation film made of, for example, an organic film or otherscontaining polyimide as a main component is formed on the emitterelectrode EE. A thickness of the insulating film FPF is, for example,about 2.5 μm.

Next, a resist film (illustration is omitted) for forming the openingportion is formed by normal lithography. Next, by, for example, dryetching, the insulating film FPF is patterned to form the openingportion OP1 (see FIG. 1) penetrating the insulating film FPF andreaching the emitter electrode EE and to form the emitter pad EP (seeFIG. 1) which is a part of the emitter electrode EE, the part beingexposed from the opening portion OP1. Then, the unnecessary resist filmfor forming the opening portion is removed by asking or others.

When the insulating film FPF is formed on the emitter electrode EE inthe cell formation region AR1 (see FIG. 1), note that the insulatingfilm FPF is formed on the gate electrode GE (see FIG. 1) in the gatewiring extraction region AR2 (see FIG. 1). Also, when the openingportion OP1 is formed in the cell formation region AR1 (see FIG. 1), theopening portion OP2 (see FIG. 1) penetrating the insulating film FPF andreaching the gate electrode GE is formed, and the gate pad GP which is apart of the gate electrode GE, the part being exposed from the openingportion OP2, is formed, in the gate wiring extraction region AR2 (seeFIG. 1).

In this manner, by steps described with reference to FIGS. 5 to 19, theelement portion PR1 is formed in the semiconductor layer SLn in each ofthe two respective hybrid cell regions LCh of the upper surface Sa ofthe semiconductor substrate SS, the two hybrid cell regions LCh beingarranged to be spaced from each other in the X axial direction when seenin a plan view. Also, the interposition portion PR2 interposed betweenthe two element portions PR1 each formed in the two hybrid cell regionsLCh is formed in the semiconductor layer SLn in the inactive cell regionLCi of the upper surface Sa of the semiconductor substrate SS, theinactive cell region being located between the two hybrid cell regionsLCh when seen in a plan view. Also, by a step illustrated in FIG. 19,the two p-type body regions, the two n⁺-type emitter regions NE, and theemitter electrode EE electrically connected to the trench electrodes TG2and TG3 included in each of the two element portions PR1 are formed. Asdescribed above, when the emitter electrode EE is formed, note that thegate electrode GE electrically connected to the trench electrode TG1included in each of the two element portions PR1 may be formed.

Next, as illustrated in FIG. 20, by performing a back grinding treatmentto the lower surface Sb of the semiconductor substrate SS, A thicknessof, for example, about 800 μm is made small to, for example, about 30 to200 μm as needed. For example, when a breakdown voltage is about 600 V,the final thickness is about 70 μm. Thus, the semiconductor layer SLp isformed inside a part of the thinned semiconductor substrate SS, the partbeing located on the lower surface Sb side with reference to thesemiconductor layer SLn. Also, chemical etching or others forelimination of damage on the lower surface Sb is performed as needed.

At this time, a semiconductor layer of the thinned semiconductorsubstrate SS is assumed to be a semiconductor layer SLp, thesemiconductor layer being located on the lower surface Sb side withreference to the semiconductor layer provided with the n-type field stopregion Ns (see FIG. 4) and being provided with the p⁺-type collectorregion CL (see FIG. 4).

Next, as illustrated in FIG. 4, an n-type impurity is doped into thelower surface Sb of the semiconductor substrate SS by, for example, ionimplantation, so that the n-type field stop region Ns is formed. Here,as for ion implantation conditions, ion implantation conditions in whichan ion species is phosphorus (P), in which the dose amount is about7×10¹² cm⁻², and in which implantation energy is about 350 keV can beexemplified as preferable conditions. Then, laser annealing or others isperformed to the lower surface Sb of the semiconductor substrate SS forimpurity activation as needed.

Next, a p-type impurity is doped into the lower surface Sb of thesemiconductor substrate SS by, for example, ion implantation, so thatthe p⁺-type collector region CL is formed. Here, as for ion implantationconditions, ion implantation conditions in which an ion species is boron(B), in which the dose amount is about 1×10¹³ cm⁻², and in whichimplantation energy is about 40 keV can be exemplified as preferableconditions. Then, laser annealing or others is performed to the lowersurface Sb of the semiconductor substrate SS for impurity activation asneeded.

That is, in the step of forming the p⁺-type collector region CL, thep-type semiconductor layer SLp is formed inside a part of thesemiconductor substrate SS, the part being located on the lower surfaceSb side with reference to the semiconductor layer SLn, and the p⁺-typecollector region CL is formed of the p-type semiconductor layer SLp.

Next, the collector electrode CE electrically connected to thesemiconductor layer SLp, that is, the p⁺-type collector region CL isformed on the lower surface Sb of the semiconductor substrate SS by, forexample, sputtering. Then, the semiconductor substrate SS is dividedinto chip regions by dicing or others and is sealed into a package asneeded, so that the semiconductor device according to the present firstembodiment is completed.

<Semiconductor Device According to First Comparative Example>

Next, a semiconductor device according to a first comparative examplewill be described. The semiconductor device according to the firstcomparative example includes an IGBT having a GG-type (gate-gate-type)active cell region. Note that the IGBT having the GG-type active cellregion means that each of two trench electrodes arranged in an activecell region to be spaced from each other is electrically connected to agate electrode.

FIG. 21 is a cross-sectional view of a principal part of thesemiconductor device according to the first comparative example.

The semiconductor device according to the first comparative exampleincludes a GG-type active cell region LCa and the inactive cell regionLCi.

The active cell region LCa is similar to the hybrid sub-cell region LCh1in the semiconductor device according to the first embodiment exceptthat the n⁺-type emitter regions NE are arranged on both sides acrossthe connection electrode CP. In the active cell region LCa, the trenchelectrode TG1 and the trench electrode TG2 are formed. However, in thefirst comparative example, the trench electrode TG2 in addition to thetrench electrode TG1 is also electrically connected to the gateelectrode GE (see FIG. 1).

Also, the n⁺-type emitter regions NE are formed in a part of thesemiconductor layer SLn, the part being located between the trench T1and the trench T2, and are arranged on both sides across the connectionelectrode CP. That is, not only the n⁺-type emitter region NE contactingthe p-type body region PB and the gate insulating film GI formed on theinner wall of the trench T1 but also the n⁺-type emitter region NEcontacting the p-type body region PB and the gate insulating film GIformed on the inner wall of the trench T2 are formed.

<Semiconductor Device According to Second Comparative Example>

Next, a semiconductor device according to a second comparative examplewill be described. The semiconductor device according to the secondcomparative example includes an IGBT having an EGE-type active cellregion.

FIG. 22 is a cross-sectional view of a principal part of thesemiconductor device according to the second comparative example. FIG.23 is a cross-sectional view of a principal part of the semiconductordevice according to the second comparative example. FIG. 23 is across-sectional view taken along a line A-A in FIG. 22.

As similar to the semiconductor device according to the firstembodiment, the semiconductor device according to the second comparativeexample is also provided with the plurality of hybrid cell regions LChserving as active cell regions and the plurality of inactive cellregions LCi. Also, each component of the hybrid cell region LCh in thesemiconductor device according to the second comparative example issimilar to each component of the hybrid cell region LCh in thesemiconductor device according to the first embodiment.

On the other hand, in the second comparative example, the two trenches14 (see FIG. 4) are not formed in the inactive cell region LCi asdifferent from the present first embodiment.

In the inactive cell region LCi in the second comparative example, thep-type body region PB is formed in an upper layer portion of a part ofthe semiconductor layer SLn, the part being located between the twoadjacent trenches T3, that is, a part of the semiconductor substrate SSon the upper surface Sa side. The p-type body region PB contacts thegate insulating film GI formed on the respective inner walls of the twotrenches T3. In the inactive cell region LCi, the p-type floating regionPF is formed in apart being located between the two adjacent trenches T3and being located on the lower surface Sb side with reference to thep-type body region PB.

That is, in the inactive cell region LCi in the second comparativeexample, the p-type floating region PF is not divided by the twotrenches T4 (see FIG. 4).

<About Characteristics of Semiconductor Device According to SecondComparative Example>

Next, characteristics of the semiconductor device according to thesecond comparative example in comparison with those of the semiconductordevice according to the first comparative example will be described.

FIG. 24 is a cross-sectional view illustrating a displacement currentpath at the time of turn-on in the semiconductor device according to thefirst comparative example to be overlapped. FIG. 25 is an equivalentcircuit diagram illustrating the displacement current path at the timeof turn-on in the semiconductor device according to the firstcomparative example. FIG. 26 is a cross-sectional view illustrating adisplacement current path at the time of turn-on in the semiconductordevice according to the second comparative example to be overlapped.FIG. 27 is an equivalent circuit diagram illustrating the displacementcurrent path at the time of turn-on in the semiconductor deviceaccording to the second comparative example.

Note that a displacement current path at the time of turn-off along withan increase of collector voltage is similar to the displacement currentpath at the time of turn-on illustrated in FIGS. 24 to 27 and has anopposite arrow direction in the displacement current.

As illustrated in FIGS. 24 and 25, in the semiconductor device accordingto the first comparative example including the IGBT having the GG-typeactive cell region, the p-type floating region PF and each of the trenchelectrodes TG1 and TG2 connected to the gate electrode GE are adjacentto each other via the gate insulating film GI. Such a semiconductordevice according to the first comparative example can be expressed by anequivalent circuit using an IGBT1 having the collector electrode CE, theemitter electrode EE, and the gate electrode GE, capacitances Cgd, Cgs,Cfpc, and Cgfp, and a resistance Rg connected to the gate electrode GE.Since displacement current CR100 generated in the active cell region LCaflows into the gate electrode GE in the semiconductor device accordingto the first comparative example, the displacement current CR100 has alarge effect on a potential of the gate electrode GE or a gatepotential.

On the other hand, as illustrated in FIGS. 26 and 27, in thesemiconductor device according to the second comparative exampleincluding the IGBT having the EGE-type active cell region, the p-typefloating region PF and the trench electrode TG1 connected to the gateelectrode GE are isolated from each other by each of the trenchelectrodes TG2 and TG3 connected to the emitter electrode EE, and arenot adjacent to each other. Such a semiconductor device according to thesecond comparative example can be expressed by an equivalent circuitusing an IGBT1 having the collector electrode CE, the emitter electrodeEE, and the gate electrode GE, capacitances Cgd, Cgs, Cfpc, Ced, andCefp, and a resistance Rg connected to the gate electrode GE. Sincedisplacement current CR1 generated in the hybrid cell region LCh flowsinto not the gate electrode GE but the emitter electrode EE in thesemiconductor device according to the second comparative example, thedisplacement current CR1 has a small effect on the potential of the gateelectrode GE or the gate potential.

Next, operations of a p-channel parasitic MOSFET (Metal OxideSemiconductor Field Effect Transistor) 2 formed in the IGBT1 will bedescribed with reference to FIG. 28. FIG. 28 is a cross-sectional viewillustrating a p-channel parasitic MOSFET in the semiconductor deviceaccording to the second comparative example.

Hereinafter, an example in which a parasitic MOSFET is formed inside theIGBT1 will be described. However, a parasitic MISFET (Metal InsulatorSemiconductor Field Effect Transistor) formed of not a MOSFET but one ofvarious MISFETs may be formed inside the IGBT1.

Also, hereinafter, operations at the time of turn-off in the L loadswitching will be considered. At the time of turn-off in the L loadswitching, a voltage VCE serving as a voltage between the collector andthe emitter increases along with the turn-off first. At this time, thechannel region of the p-channel parasitic MOSFET 2 is inverted intop-type. And, holes serving as carriers accumulated in the p-typefloating region PF and the n⁻-type drift region ND are discharged viathe p-channel parasitic MOSFET 2. Since the accumulated holes arepromptly discharged by the above-described operations, the semiconductordevice according to the second comparative example has characteristicsin which the switching speed is higher than that of the semiconductordevice according to the first comparative example.

<Regarding Problems of Semiconductor Device According to SecondComparative Example>

On the other hand, the semiconductor device including the IGBT havingthe EGE-type active cell region (semiconductor device according to thesecond comparative example) has problems. Hereinafter, problems of thesemiconductor device according to the second comparative example will bedescribed.

First, a rapid change or oscillation of current flowing in the IGBT atthe time of turn-on will be described.

As described above, as a merit of the semiconductor device including theIGBT having the EGE-type active cell region, the semiconductor devicehas characteristics of the high switching speed. Meanwhile, depending ona field of an electronic system using the semiconductor device accordingto the second comparative example, the current flowing in the IGBTrapidly changes at the time of turn-on in a mismatch between thesemiconductor device according to the second comparative example and acircuit connected to the semiconductor device according to the secondcomparative example, that is, when the switching speed of thesemiconductor device according to the second comparative example is toohigh, and therefore, oscillation is observed in a switching waveform insome cases. In order to prevent or suppress such oscillation in theswitching waveform, it is required to adjust a gate capacitance Qg so asto slightly increase.

For example, in a switching waveform obtained when the semiconductordevice according to the second comparative example is turned on so thata rated current flows, no oscillation is observed at the time ofturn-on. However, in a switching waveform obtained when thesemiconductor device is turned on so that a current as low as about 1/10of the rated current flows, oscillation, that is, ringing is observed atthe time of turn-on in some cases. That is, the lower the currentflowing in the electronic system using the semiconductor deviceaccording to the second comparative example is, the more easily theoscillation, that is, the ringing is observed at the time of turn-on.

When the oscillation is observed at the time of turn-on as describedabove, there is a risk of occurrence of an EMI (Electro MagneticInterference) noise or others. Thus, it is desired to increase the gatecapacitance Qg to prevent or suppress the rapid change of the currentflowing in the IGBT at the time of turn-on, that is, an increase of achange rate (di/dt) of the current “i” flowing in the IGBT with respectto the time “t”. However, in the semiconductor device according to thesecond comparative example, it is difficult to easily increase the gatecapacitance Qg, and therefore, it is difficult to prevent or suppressthe rapid change of th current flowing in the IGBT at the time ofturn-on.

Next, a switching loss at the time of turn-on will be described withreference to FIG. 29. FIG. 29 is a cross-sectional view of a principalpart of the semiconductor device according to the second comparativeexample. FIG. 29 illustrates a current path PT101 of the hole currentflowing in the p-type floating region PF, that is, the p-channelparasitic MOSFET, at the time of turn-on, to be schematicallyoverlapped.

In the semiconductor device including the IGBT, the carriers can beaccumulated early at the time of turn-on when the IE effect is large,and therefore, the switching loss at the time of turn-on can bedecreased.

However, in the semiconductor device including the IGBT having theEGE-type active cell region, the holes serving as the carriers aredischarged via the p-channel parasitic MOSFET at the time of turn-on,the IE effect is small, and the switching loss at the time of turn-onincreases. This means that the potential of the channel region of thep-channel parasitic MOSFET rises at the time of turn-on of the IGBTincluded in the semiconductor device, which results in an ON state ofthe parasitic MOSFET to discharge the holes serving as the carriers.Specifically, as illustrated in FIG. 29, at the time of turn-on in thesecond comparative example, the hole current flows in the current pathPT101 through the n⁻-type drift region ND, the p-type floating regionPF, and parts of the p-type floating region PF, the n-type hole barrierregion NHB, and the p-type body region PB, the parts being close to eachof the trench electrodes TG2 and TG3.

Although illustration is omitted, by calculation of a switching waveformat the time of turn-on by the use of TCAD (Technology Computer-AidedDesign), it has been confirmed that the potential of the channel regionof the p-channel parasitic MOSFET rises at the time of turn-on of theIGBT, which results in the discharge of the holes serving as thecarriers. Also, by calculation of a hole concentration distribution inthe semiconductor device at the time of turn-on by the use of the TCAD,it has been confirmed that the holes serving as the carriers aredischarged via the p-channel parasitic MOSFET at the time of turn-on ofthe IGBT.

In this manner, in the semiconductor device including the IGBT havingthe EGE-type active cell region (semiconductor device according to thesecond comparative example), the holes serving as the carriers aredischarged via the p-channel parasitic MOSFET at the time of turn-on,and therefore, it is difficult to decrease the switching loss at thetime of turn-on.

As described above, in the semiconductor device including the IGBThaving the EGE-type active cell region (semiconductor device accordingto the second comparative example), it is desired to prevent or suppressthe rapid change of the current flowing in the IGBT at the time ofturn-on and to decrease the switching loss at the time of turn-on.

<Main Characteristics and Effects of Present Embodiment>

The semiconductor device according to the present first embodimentincludes the element portion PR1 provided in the hybrid cell region LChserving as the EGE-type active cell region and the interposition portionPR2 provided in the inactive cell region LCi. The p-type floating regionPF included in the interposition portion PR2 interposed between the twoadjacent element portions PR1 is divided into two by the two trenchesT4.

Specifically, the interposition portion PR2 provided in the inactivecell region LCi includes the p-type body region PB1 formed in a part ofthe semiconductor layer SLn, the part being located between the twotrenches T4. The interposition portion PR2 provided in the inactive cellregion LCi includes the two p-type floating regions PF1 formed in thetwo respective parts of the semiconductor layer SLn, the two parts beinglocated on both sides of the p-type body region PB1 via the tworespective trenches T4. The end portion of each of the two p-typefloating regions PF1 on the lower surface Sb side is arranged on thelower surface Sb side in the Z axial direction with reference to the endportion of the p-type body region PB1 on the lower surface Sb side.

According to such a semiconductor device of the present firstembodiment, the charge amount obtained when the gate voltage issaturated to the maximum value, that is, the gate charge amount in theswitching waveform at the time of turn-on is larger than that in thesemiconductor device of the second comparative example. That is,according to the semiconductor device of the present first embodiment,by newly providing the two trench electrodes TG4, the gate capacitancecan be increased more than that of the semiconductor device of thesecond comparative example, so that the rapid change or the oscillationof the current flowing in the IGBT at the time of turn-on can beprevented or suppressed.

Also, according to such a semiconductor device of the present firstembodiment, a width in the X axial direction of apart (p-type floatingregion PF1) of the p-type floating region PF, the part contacting thetrench T3, can be shorter than that in the semiconductor device of thesecond comparative example without shortening the width Wi (see FIG. 2)of the inactive cell region LCi. Accordingly, according to thesemiconductor device of the present first embodiment, a magnitude of thehole current flowing in the p-type floating region PF, that is, thep-channel parasitic MOSFET is smaller at the time of turn-on than thatin the semiconductor device of the second comparative example. Further,according to such a semiconductor device of the present firstembodiment, the hole concentration accumulated in the n-type holebarrier region NHB of the semiconductor layer SLn and a part (n⁻-typedrift region ND) of the semiconductor layer SLn, the part being locatedon the lower surface Sb side with reference to the n-type hole barrierregion NHB, is lower at the time of turn-on than that in thesemiconductor device of the second comparative example. Accordingly,according to the semiconductor device of the present first embodiment,the IE effect can be enhanced further than that in the semiconductordevice of the second comparative example, and the switching loss at thetime of turn-on in the L load switching can be further decreased.

FIG. 30 is a cross-sectional view of a principal part of thesemiconductor device according to the first embodiment. FIG. 30illustrates a current path PT1 of the hole current flowing in the p-typefloating region PF1, that is, the p-channel parasitic MOSFET, at thetime of turn-on, to be schematically overlapped. In FIGS. 29 and 30,note that the magnitude of the hole current in the second comparativeexample and the first embodiment is expressed by a magnitude of thewidth of the schematically-illustrated current path PT1.

As illustrated in FIG. 30, also in the present first embodiment, at thetime of turn-on, the hole current flows in the current path PT1 passingfrom the n⁻-type drift region ND to the p-type floating region PF, andbesides, passing through parts of the p-type floating region PF, then-type hole barrier region NHB, and the p-type body region PB, the partsbeing close to each of the trench electrodes TG2 and TG3.

However, in comparison between FIG. 29 and FIG. 30, it has been foundthat the magnitude of the hole current flowing in the p-type floatingregion PF, that is, the p-channel parasitic MOSFET, is smaller in thepresent first embodiment than that in the second comparative example. Itis considered that this is because the hole current expressed by acurrent path PT2 does not reach the emitter electrode EE in the partLCi2 included in the inactive cell region LCi.

In the semiconductor device according to the present first embodiment,note that the collector voltage VCE in the switching waveform at thetime of turn-on decreases faster than that in the semiconductor deviceaccording to the second comparative example. Thus, according to thesemiconductor device of the present first embodiment, the amount of theholes serving as the carriers to be discharged at the time of turn-onvia the p-type floating region PF, that is, the p-channel parasiticMOSFET, can be suppressed further than that in the semiconductor deviceof the second comparative example, the IE effect can be improved, and anon-voltage can be decreased.

That is, in the semiconductor device according to the present firstembodiment, a performance of a semiconductor device such as the IEeffect can be improved more than that in the semiconductor deviceaccording to the second comparative example.

In the technique disclosed in the above-described Patent Document 3,note that the second trench having the buried first electrical conductorconnected to an emitter electrode between two active cell regions.However, each of the active cell regions is not the EGE-type hybrid cellregion but the GG-type active cell region described in the firstcomparative example. Also, in the technique disclosed in theabove-described Patent Document 3, a lower surface of a floating p-typelayer formed between the first trench and the second trench adjacent toeach other is not arranged closer to a lower side than a lower surfaceof a floating p-type layer formed between the two second trenches.

FIG. 31 is a cross-sectional view illustrating a snubber circuit formedin the semiconductor device according to the first embodiment to beoverlapped. FIG. 32 is an equivalent circuit diagram of the IGBT towhich the snubber circuit is connected.

As illustrated in FIGS. 31 and 32, the two trench electrodes TG4electrically connected to the emitter electrode EE are formed in theinactive cell region LCi, and the p-type floating region PF is dividedby the two trench electrodes TG4, so that the IGBT1 is connected inparallel with a parasitic snubber portion CS serving as a snubbercircuit. By the parallel connection of the IGBT1 with the parasiticsnubber portion CS as described above, an effect of absorbing a rapidvoltage change, that is, an effect of absorbing a large dv/dt even in alarge change rate (dv/dt) of the voltage “v” with respect to the time“t”, can be expected, and, for example, the EMI noise or othersgenerated in the semiconductor device according to the present firstembodiment can be decreased.

In the present first embodiment, note that the conductivity types of therespective semiconductor regions may be collectively changed to oppositeconductivity types (the same goes for the following modification exampleand second embodiment).

<Modification Example of Semiconductor Device According to FirstEmbodiment>

In the semiconductor device according to the first embodiment, in thepart LCi2 included in the inactive cell region LCi, the n⁻-type driftregion ND is formed in a part of the semiconductor layer SLn, the partbeing located between the two trenches T4 and being located on the lowersurface Sb side with reference to the p-type body region PB1.

However, in the part LCi2 included in the inactive cell region LCi, anelectron accumulation region EA serving as an n-type semiconductorregion may be formed in a part of the semiconductor layer SLn, the partbeing located between the two trenches T4 and being located on the lowersurface Sb side with reference to the p-type body region PB1. Such anexample will be described as a modification example of the semiconductordevice according to the first embodiment.

FIG. 33 is a cross-sectional view of a principal part of a semiconductordevice according to a modification example of the first embodiment. Notethat FIG. 33 corresponds to a cross-sectional view taken along a lineA-A in FIGS. 2 and 3.

The semiconductor device according to the present modification examplehas a similar structure to that of the semiconductor device according tothe first embodiment except that, in the part LCi2 included in theinactive cell region LCi, the electron accumulation region EA serving asan n-type semiconductor region is formed in a part of the semiconductorlayer SLn, the part being located between the two trenches T4 and beinglocated on the lower surface Sb side with reference to the p-type bodyregion PB1. Thus, the semiconductor device according to the presentmodification example has a similar effect to that of the semiconductordevice according to the first embodiment.

On the other hand, in the present modification example, as differentfrom the first embodiment, in the part LCi2 included in the inactivecell region LCi, the electron accumulation region EA is formed in thepart of the semiconductor layer SLn, the part being located between thetwo trenches 14 and being located on the lower surface Sb side withreference to the p-type body region PB1. That is, the interpositionportion PR2 includes the electron accumulation region EA. The n-typeimpurity concentration in the electron accumulation region EA is higherthan the n-type impurity concentration in a part (n⁻-type drift regionND) of the semiconductor layer SLn, the part being located on the lowersurface Sb side with reference to the electron accumulation region EA.

In the present modification example, electrons are supplied from theelectron accumulation region EA at the time of turn-on. In the presentmodification example, this manner can increase the amount of electronsto be supplied to a part (n⁻-type drift region ND) of the semiconductorlayer SLn, the part being located below the p-type floating region PF1,more than the first embodiment, can more improve a function of a p/n/pbipolar transistor included in the IGBT, and can more improve the IEeffect of the IGBT.

Also, in the present modification example, electrons are supplied fromthe electron accumulation region EA also at the time of turn-off. Thus,in the present modification example, the holes serving as the carrierswhich are accumulated in the n⁻-type drift region ND at the time ofturn-on, that is, at the time of conduction, and which are dischargedthrough the p-channel parasitic MOSFET at the time of turn-off arerecombined with the electrons supplied from the electron accumulationregion EA, and thus, can be eliminated rapidly, so that the operationspeed at the time of turn-off can be increased.

Each of FIGS. 34 to 37 is a cross-sectional view of a principal partillustrating a step of manufacturing the semiconductor device accordingto the modification example of the first embodiment. Each of FIGS. 34 to37 corresponds to a cross-sectional view taken along a line A-A in FIGS.2 and 3 as similar to FIG. 33.

In the step of manufacturing the semiconductor device according to thepresent modification example, a similar step to, for example, a stepdescribed with reference to FIG. 5 in the step of manufacturing thesemiconductor device according to the first embodiment is performed toprepare the semiconductor substrate SS.

Next, in the present modification example, the electron accumulationregion EA is formed. For example, when a similar step to a stepdescribed with reference to FIG. 5 in the first embodiment is performedto form the n-type hole barrier region NHB, the electron accumulationregion EA is formed in the part LCi2 included in the inactive cellregion LCi by, for example, ion implantation while using the patternedresist film R1 as a mask as illustrated in FIG. 34. As for ionimplantation conditions at this time, similar ion implantationconditions to those when the n-type hole barrier region NHB is formedcan be used.

Next, in the present modification example, similar steps to thosedescribed with reference to FIGS. 6 to 10 in the first embodiment areperformed to form the trenches T1, T2, T3, and T4 as illustrated in FIG.35. At this time, in the part LCi2 included in the inactive cell regionLCi, the electron accumulation region EA is formed in a part of thesemiconductor layer SLn on the upper surface Sa side, the part beinglocated between the two trenches T4.

Next, in the present modification example, drive-in diffusion (forexample, at 1200° C. for about 30 minutes) is performed to the electronaccumulation region EA. For example, when a similar step to a stepdescribed with reference to FIG. 11 in the first embodiment is performedto perform drive-in diffusion for the p-type floating regions PF and then-type hole barrier regions NHB, drive-in diffusion is performed for theelectron accumulation region EA as illustrated in FIG. 36. At this time,in the part LCi2 included in the inactive cell region LCi, the electronaccumulation region EA is formed in a part of the semiconductor layerSLn, the part being located between the two trenches T4.

Next, in the present modification example, similar steps to stepsdescribed with reference to FIGS. 12 to 15 in the first embodiment areperformed to form the p-type body region PB as illustrated in FIG. 37.At this time, in the part LCi2 included in the inactive cell region LCi,the p-type body region PB1 serving as the p-type body region PB isformed in a part of the semiconductor layer SLn on the upper surface Saside, the part being located between the two trenches T4, so as tocontact the gate insulating film GI formed on each inner wall of the twotrenches T4. The electron accumulation region EA is formed in a part ofthe semiconductor layer SLn, the part being located between the twotrenches T4 and being located on the lower surface Sb side withreference to the p-type body region PB1.

In the step of manufacturing the semiconductor device according to thepresent modification example, when the n-type hole barrier regions NHBis formed in each of the hybrid sub-cell regions LCh1 and LCh2, theelectron accumulation region EA can be formed in the inactive cellregion LCi. Thus, in the step of manufacturing the semiconductor deviceaccording to the present modification example, it is not required toprepare an additional mask for forming the electron accumulation regionEA, and it is not required to perform additional lithography for formingthe electron accumulation region EA.

Then, similar steps to steps described with reference to FIGS. 16 to 20and 4 in the first embodiment are performed, so that the semiconductordevice according to the present modification example is completed.

Second Embodiment

In a second embodiment, the examination is made about division of thep-type floating region PF into three by the two trenches T4 and twotrenches T5 in the inactive cell region LCi located between the twoadjacent hybrid cell regions LCh.

<Configuration of Semiconductor Device>

FIG. 38 is a cross-sectional view of a principal part of a semiconductordevice according to the second embodiment. Note that FIG. 38 correspondsto a cross-sectional view taken along a line A-A in FIGS. 2 and 3.

The semiconductor device according to the present second embodiment hasa similar structure to that of the semiconductor device according to thefirst embodiment except that the p-type floating region PF is dividedinto three by the two trenches T4 and the two trenches T5 in theinactive cell region LCi located between the two adjacent hybrid cellregions LCh. Thus, the semiconductor device according to the presentsecond embodiment has a similar effect to that of the semiconductordevice according to the first embodiment.

In the present second embodiment, as similar to the first embodiment,the interposition portion PR2 formed in the inactive cell region LCiincludes the two trenches T4, the two trench electrodes TG4, the twop-type floating regions PF1, and the p-type body region PB1.

On the other hand, in the present second embodiment, as different fromthe first embodiment, the interposition portion PR2 formed in theinactive cell region LCi includes the two trenches T5, two trenchelectrodes TG5, and a p-type floating region PF2 serving as the p-typefloating region PF. Thus, in the present second embodiment, as differentfrom the first embodiment, the p-type floating region PF is divided intotwo p-type floating regions PF1 and one p-type floating region PF2 bythe two trenches 14 and the two trenches T5 in the inactive cell regionLCi.

The two trenches T5 serving as trench portions are formed on the uppersurface Sa side of the semiconductor substrate SS in the inactive cellregion LCi. The two trenches T5 each reach the middle of thesemiconductor layer SLn from the upper surface Sa of the semiconductorsubstrate SS, each extend in the Y axial direction when seen in a planview, and are arranged to be spaced from each other in the X axialdirection between the two trenches 14.

On each of inner walls of the two trenches T5, the gate insulating filmGI is formed. Inside each of the two trenches T5, the trench electrodeTG5 is formed on the gate insulating film GI so as to bury the trenchT5. That is, each of the two trench electrodes TG5 is buried inside eachof the trenches T5 via the gate insulating film GI. The trenchelectrodes TG5 are electrically connected to the emitter electrode EE.That is, the two trench electrodes TG5 included in the interpositionportion PR2 are electrically connected to the emitter electrode EE. Notethat each of the two trench electrodes TG5 is formed continuously alongthe Y axial direction when seen in a plan view.

In the inactive cell region LCi, the p-type body region PB is formed ina part of the semiconductor layer SLn on the upper surface Sa side, thepart being located between the two trenches T5. The p-type body regionPB contacts the gate insulating film GI formed on each of the innerwalls of the two trenches T5.

In the inactive cell region LCi, the p-type floating region PF2 servingas the p-type floating region PF, which is a p-type semiconductorregion, is formed in a part of the semiconductor layer SLn, the partbeing located between the two trenches T5 and being located below thep-type body region PB.

Also, in the inactive cell region LCi, the p-type body region PB11serving as the p-type body region PB1 is formed in a part of thesemiconductor layer SLn on the upper surface Sa side, the part beinglocated between the trench T4 and the trench T5 adjacent to each other.However, in the inactive cell region LCi, the p-type floating region PFis not formed in apart of the semiconductor layer SLn, the part beinglocated between the trench 14 and the trench T5 adjacent to each otherand being located below the p-type body region PB.

That is, the interposition portion PR2 provided in the inactive cellregion LCi includes the p-type floating region PF2 formed in a part ofthe semiconductor layer SLn, the part being located between the twotrenches T5. The interposition portion PR2 provided in the inactive cellregion LCi also includes the two p-type body regions PB11 each formed intwo parts of the semiconductor layer SLn, the parts being located onboth sides of the p-type floating region PF2 in the X axial directionvia the two respective trenches T5.

The p-type body region PB1 is assumed to be formed of the two p-typebody regions PB11. At this time, the p-type body region PB1 includes thetwo p-type body regions PB11, and the p-type body region PB1 includingthe two p-type body regions PB11 is formed in a part of thesemiconductor layer SLn, the part being located between the two trenches14, as similar to the first embodiment.

In the present second embodiment, as similar to the first embodiment,each of two parts of the inactive cell region LCi, each of the two partsbeing located between the trench T3 and trench T4 adjacent to eachother, is referred to as the part LCi1. Also, a part of the inactivecell region LCi, the part being located between the two trenches 14, isreferred to as the part LCi2.

On the other hand, in the present second embodiment, as different fromthe first embodiment, in the part LCi2, a part of located between theadjacent trench 14 and trench T5 is referred to as a part LCi21. Also,in the present second embodiment, as different from the firstembodiment, a part of the part LCi2, the part being located between thetwo trenches T5 is referred to as a part LCi22.

At this time, an end portion (lower end), on the lower surface Sb side,of each of the two p-type floating regions PF1 formed in the tworespective parts LCi1 is arranged on the lower surface Sb side (lowerside) in the Z axial direction with reference to both end portions(lower ends), on the lower surface Sb side, of the two p-type bodyregions PB11 each formed in the two respective parts LCi21. Also, an endportion (lower end), on the lower surface Sb side, of the p-typefloating region PF2 formed in the part LCi22 is arranged on the lowersurface Sb side (lower side) in the Z axial direction with reference toboth end portions (lower ends), on the lower surface Sb side, of the twop-type body regions PB11 formed in the two respective parts LCi21. Inother words, the lower end of each of two p-type floating regions PF1and one p-type floating region PF2 is arranged on the lower side in theZ axial direction with reference to both lower ends of the tworespective p-type body regions PB11. In each of the two parts LCi21, then⁻-type drift region ND is formed in a part of the semiconductor layerSLn, the part being located below the p-type body region PB11.

<Method of Manufacturing Semiconductor Device>

In a method of manufacturing the semiconductor device according to thesecond embodiment, as different from the first embodiment, in the stepof forming the two trenches 14, the two trenches T5 each of whichreaches the middle of the semiconductor layer SLn from the upper surfaceSa of the semiconductor substrate SS, each of which extends in the Yaxial direction when seen in a plan view, and which are arranged to bespaced from each other between the two trenches 14 in the X axialdirection are formed.

Also, in the method of manufacturing the semiconductor device accordingto the present second embodiment, as different from the method ofmanufacturing the semiconductor device according to the firstembodiment, in the step of forming the two trench electrodes TG4, thetwo trench electrodes TG5 which are buried inside the two respectivetrenches T5 via the gate insulating film GI are formed.

Also, in the method of manufacturing the semiconductor device accordingto the present second embodiment, as different from the method ofmanufacturing the semiconductor device according to the firstembodiment, in the step of forming the two p-type floating regions PF1,the p-type floating region PF2 is formed in a part of the semiconductorlayer SLn, the part being located between the two trenches T5. And, inthe inactive cell region LCi, the two p-type body regions PB11 areformed in two parts of the semiconductor layer SLn, the two parts beinglocated on both sides of the p-type floating region PF2 in the X axialdirection via the two respective trenches T5. The two p-type bodyregions PB11 are included in the p-type body region PB1.

At this time, the p-type floating region PF2 and the two p-type bodyregions PB11 are formed so that the end portion, on the lower surface Sbside, of each of two p-type floating regions PF1 and one p-type floatingregion PF2 is arranged on the lower surface Sb side in the Z axialdirection with reference to both end portions, on the lower surface Sbside, of the two respective p-type body regions PB11.

Also, in the method of manufacturing the semiconductor device accordingto the present second embodiment, as different from the method ofmanufacturing the semiconductor device according to the firstembodiment, the emitter electrode EE electrically connected to the twotrench electrodes TG5 included in the interposition portion PR2 isformed as the emitter electrode EE.

Except the above-described points, the method of manufacturing thesemiconductor device according to the present second embodiment can besimilar to the method of manufacturing the semiconductor deviceaccording to the first embodiment.

<Main Characteristics and Effects of Present Embodiment>

As similar to the semiconductor device according to the firstembodiment, the semiconductor device according to the present secondembodiment includes the element portion PR1 provided in the hybrid cellregion LCh serving as the EGE-type active cell region and theinterposition portion PR2 provided in the inactive cell region LCi. Onthe other hand, in the second embodiment as different from the firstembodiment in which the p-type floating region PF is divided into two,the p-type floating region PF included in the interposition portion PR2interposed between the two adjacent element portions PR1 is divided intothree by the two trenches T4 and the two trenches T5.

Specifically, the interposition portion PR2 provided in the inactivecell region LCi includes not only the two p-type floating regions PF1but also the p-type floating region PF2 formed in apart of thesemiconductor layer SLn, the part being located between the two trenchesT5, and the two p-type body regions PB11 formed in two parts of thesemiconductor layer SLn, the two parts being located on both sides ofthe p-type floating region PF2 via the two respective trenches T5. Theend portion, on the lower surface Sb side, of each of two p-typefloating regions PF1 and one p-type floating region PF2 is arranged onthe lower surface Sb side in the Z axial direction with reference toboth end portions, on the lower surface Sb side, of the two p-type bodyregions PB11.

According to such a semiconductor device of the present secondembodiment, the charge amount obtained when the gate voltage issaturated to the maximum value, that is, the gate charge amount in theswitching waveform at the time of turn-on is larger than that in thesemiconductor device of the first embodiment. That is, according to thesemiconductor device of the present second embodiment, by newlyproviding the two trench electrodes TG5 in addition to the two trenchelectrodes TG4, the gate capacitance can be increased more than that ofthe semiconductor device of the first embodiment, so that the rapidchange or the oscillation of the current flowing in the IGBT at the timeof turn-on can be further prevented or suppressed.

Also, according to such a semiconductor device of the present secondembodiment, a width in the X axial direction of a part (p-type floatingregion PF1) of the p-type floating region PF, the part contacting thetrench T3, can be shorter than that in the semiconductor device of thefirst embodiment without shortening the width Wi (see FIG. 2) of theinactive cell region LCi. Accordingly, according to the semiconductordevice of the present second embodiment, a magnitude of the hole currentflowing in the p-type floating region PF, that is, the p-channelparasitic MOSFET is further smaller at the time of turn-on than that inthe semiconductor device of the first embodiment. Accordingly, accordingto the semiconductor device of the present second embodiment, the IEeffect can be enhanced still further than that in the semiconductordevice of the first embodiment, the on voltage can be further reduced,and the switching loss at the time of turn-on in the L load switchingcan be still further decreased.

Third Embodiment

In a third embodiment, the explanation will be made about thesemiconductor device including the IGBT having the EGE-type active cellregion in which the width of the active cell region is small, and inwhich the connection electrode and the trench electrode overlap whenseen in a plan view.

<Configuration of Semiconductor Device>

First, a configuration of a semiconductor device according to thepresent third embodiment will be described.

A structure of the semiconductor device according to the present thirdembodiment is similar to the structure of the semiconductor deviceaccording to the first embodiment except that the connection electrodeCP and each of the trench electrodes TG2 and TG3 overlap when seen in aplan view. Accordingly, hereinafter, different points from those in thestructure of the semiconductor device according to the first embodimentwill be described mainly.

FIG. 39 is a plan view of a principal part of the semiconductor deviceaccording to the third embodiment. FIG. 40 is a cross-sectional view ofa principal part of the semiconductor device according to the thirdembodiment. FIG. 40 is a cross-sectional view taken along a line A-A inFIG. 39.

In the semiconductor device according to the present third embodiment,as similar to the semiconductor device according to the firstembodiment, the plurality of n⁺-type emitter regions NE are formed ineach of the hybrid sub-cell regions LCh1 and LCh2.

Also, in the semiconductor device according to the present thirdembodiment, as similar to the semiconductor device according to thefirst embodiment, the p⁺-type semiconductor region PR is formedcontinuously along the Y axial direction in the hybrid sub-cell regionLCh1. Also, in the hybrid sub-cell region LCh1, the contact trench CTserving as an opening portion is formed continuously along the Y axialdirection in the p-type body region PB. The contact trench CT reachesthe p⁺-type body contact region PBC arranged in the hybrid sub-cellregion LCh1.

Also, in the semiconductor device according to the present thirdembodiment, as similar to the semiconductor device according to thefirst embodiment, the p⁺-type semiconductor region PR is formedcontinuously along the Y axial direction in the hybrid sub-cell regionLCh2. Also, in the hybrid sub-cell region LCh2, the contact trench CTserving as an opening portion is formed continuously along the Y axialdirection in the p-type body region PB. The contact trench CT reachesthe p⁺-type body contact region PBC arranged in the hybrid sub-cellregion LCh2.

On the other hand, in the semiconductor device according to the presentthird embodiment as different from the semiconductor device according tothe first embodiment, the contact trench CT overlaps with the trench T2in the hybrid sub-cell region LCh1 when seen in a plan view, and thecontact trench CT overlaps with the trench T3 in the hybrid sub-cellregion LCh2 when seen in a plan view.

Also, the p⁺-type semiconductor region PR may contact the gateinsulating film GI formed on the inner wall of the trench T2 in thehybrid sub-cell region LCh1, and the p⁺-type semiconductor region PR maycontact the gate insulating film GI formed on the inner wall of thetrench T3 in the hybrid sub-cell region LCh2.

<Method of Manufacturing Semiconductor Device>

A method of manufacturing the semiconductor device according to thepresent third embodiment is similar to the method of manufacturing thesemiconductor device according to the first embodiment explained withreference to FIGS. 5 to 20 except that the connection electrode CP andeach of the trench electrodes TG2 and TG3 overlap when seen in a planview. Accordingly, hereinafter, different points from those in thestructure of the semiconductor device according to the first embodimentwill be described mainly.

That is, in a step of manufacturing the semiconductor device accordingto the present third embodiment, the contact trench CT is formed so asto overlap with the trench T2 in the hybrid sub-cell region LCh1 whenseen in a plan view, and the contact trench CT is formed so as tooverlap with the trench T3 in the hybrid sub-cell region LCh2 when seenin a plan view.

In the present third embodiment as different from the first embodiment,note that, in each of the hybrid sub-cell regions LCh1 and LCh2, thecontact trench CT is formed continuously along the Y axial directionwhen seen in a plan view, and the p⁺-type semiconductor region PR isformed continuously along the Y axial direction when seen in a planview.

<Main Characteristics and Effects of Present Embodiment>

In the semiconductor device according to the present third embodiment,as similar to the semiconductor device according to the firstembodiment, the p-type floating region PF included in the interpositionportion PR2 interposed between the two adjacent element portions PR1 isdivided into two by the two trenches 14.

Accordingly, in the present third embodiment, as similar to the firstembodiment, the gate capacitance can be increased, and the rapid changeor oscillation of current flowing in the IGBT at the time of turn-on canbe prevented or suppressed. Also, the IE effect can be enhanced, theon-voltage can be decreased, and the switching loss at the time ofturn-on in the L load switching can be decreased.

On the other hand, in the present third embodiment, as different fromthe first embodiment, the connection electrode CP and the trenchelectrode TG2 formed in the hybrid sub-cell region LCh1 overlap whenseen in a plan view, and the connection electrode CP and the trenchelectrode TG3 formed in the hybrid sub-cell region LCh2 overlap. Thatis, in the present third embodiment, each width of parts of thesemiconductor layer SLn, the parts being between the trench T1 and thetrench T2 and between the trench T1 and the trench T3, are shorter thanthose of the first embodiment.

Thus, in the present third embodiment, hole discharge resistance ishigher than that in the first embodiment, the holes are easy to beaccumulated in a part of the n⁻-type drift region ND on the emitterelectrode EE side, an implantation efficiency of the electrons from theemitter electrode EE can be increased, and the IE effect can be furtherenhanced. Accordingly, in the present third embodiment, performance ofthe semiconductor device can be further improved than that in the firstembodiment.

Fourth Embodiment

The IGBT chip provided in the semiconductor device according to thefirst embodiment is a semiconductor device as an IGBT chip having anEGE-type active cell region, and the p⁺-type semiconductor region PR isformed continuously along the Y axial direction in each of the hybridcell regions LCh.

On the other hand, since the IGBT chip provided in the semiconductordevice according to the first embodiment may be only required to be asemiconductor device as an IGBT chip having an EGE-type active cellregion, a plurality of p⁺-type semiconductor regions PR may be arrangedto be spaced from each other in the Y axial direction in each of thehybrid cell regions LCh. Such an example will be described as asemiconductor device according to a fourth embodiment.

Each of FIGS. 41 and 42 is a plan view of a principal part of thesemiconductor device according to the fourth embodiment. Each of FIGS.43 and 44 is a cross-sectional view of a principal part of thesemiconductor device according to the fourth embodiment. FIG. 45 is theillustration for comparison, and is a cross-sectional view of aprincipal part of the semiconductor device according to the firstembodiment. FIG. 43 is a cross-sectional view taken along a line B-B inFIG. 42, FIG. 44 is a cross-sectional view taken along a line C-C inFIG. 42, and FIG. 45 is a cross-sectional view taken along a line C-C inFIG. 3. Note that each cross-sectional view taken along a line A-Aillustrated in FIGS. 41 and 42 is similar to the cross-sectional viewillustrated in FIG. 4.

In the present fourth embodiment, in the hybrid sub-cell region LCh1, aplurality of p⁺-type semiconductor regions PR each including the p⁺-typebody contact region PBC and the p⁺-type latch-up prevention region PLPare provided. In the hybrid sub-cell region LCh1, each of the pluralityof p⁺-type semiconductor regions PR is formed in apart of thesemiconductor layer SLn, the part being located between the trench T1and the trench T2, and contacts the p-type body region PB. In the hybridsub-cell region LCh1, the p-type impurity concentration in the pluralityof p⁺-type semiconductor regions PR is higher than the p-type impurityconcentration in the p-type body region PB. The emitter electrode EE iselectrically connected to the p-type body region PB via the plurality ofp⁺-type semiconductor regions PR.

In the hybrid sub-cell region LCh1, the plurality of p⁺-typesemiconductor regions PR are arranged to be spaced from each other inthe Y axial direction when seen in a plan view. Accordingly, theon-voltage of the semiconductor chip CHP can be decreased, and theswitching loss at the time of turn-on in the L load switching can bedecreased.

Also, in the hybrid sub-cell region LCh1, the plurality of contacttrenches CT serving as opening portions are formed in the interlayerinsulating film IL and the p-type body region PB. The plurality ofcontact trenches CT are arranged to be spaced from each other in the Yaxial direction when seen in a plan view. In each of the plurality ofcontact trenches CT, each of the plurality of connection electrodes CPis buried. Also, in the hybrid sub-cell region LCh1, the emitterelectrode EE is electrically connected to the n⁺-type emitter region NEand the plurality of p⁺-type semiconductor regions PR via the pluralityof connection electrodes CP.

Also, in the present fourth embodiment, in the hybrid sub-cell regionLCh2, the plurality of p⁺-type semiconductor regions PR each includingthe p⁺-type body contact region PBC and the p⁺-type latch-up preventionregion PLP are provided. In the hybrid sub-cell region LCh2, each of theplurality of p⁺-type semiconductor regions PR is formed in apart of thesemiconductor layer SLn, the part being located between the trench T1and the trench T3, and contacts the p-type body region PB. In the hybridsub-cell region LCh2, the p-type impurity concentration in the pluralityof p⁺-type semiconductor regions PR is higher than the p-type impurityconcentration in the p-type body region PB. The emitter electrode EE iselectrically connected to the p-type body region PB via the plurality ofp⁺-type semiconductor regions PR.

In the hybrid sub-cell region LCh2, the plurality of p⁺-typesemiconductor regions PR are arranged to be spaced from each other inthe Y axial direction when seen in a plan view. Accordingly, theon-voltage of the semiconductor chip CHP can be decreased, and theswitching loss at the time of turn-on in the L load switching can bedecreased.

Also, in the hybrid sub-cell region LCh2, the plurality of contacttrenches CT serving as opening portions are formed in the interlayerinsulating film IL and the p-type body region PB. The plurality ofcontact trenches CT are arranged to be spaced from each other in the Yaxial direction when seen in a plan view. In each of the plurality ofcontact trenches CT, each of the plurality of connection electrodes CPis buried. Also, in the hybrid sub-cell region LCh2, the emitterelectrode EE is electrically connected to the n⁺-type emitter region NEand the p⁺-type semiconductor regions PR via the plurality of connectionelectrodes CP.

As illustrated in FIG. 44, in each of the hybrid sub-cell regions LCh1and LCh2, a region provided with the p⁺-type semiconductor region PR inthe Y axial direction, that is, an active section LCba, and a region notprovided with the p⁺-type semiconductor region PR in the Y axialdirection, that is, an inactive section LCbi, are alternately arranged.

Preferably, in the present fourth embodiment, in the hybrid sub-cellregion LCh1, each of the plurality of n⁺-type emitter regions NE isarranged at the same position as that of each of the plurality ofp⁺-type semiconductor regions PR in the Y axial direction. Also,preferably, in the present fourth embodiment, in the hybrid sub-cellregion LCh2, each of the plurality of n⁺-type emitter regions NE isarranged at the same position as that of each of the plurality ofp⁺-type semiconductor regions PR in the Y axial direction.

As described above with reference to FIGS. 2 and 3, and as illustratedin FIG. 45, note that, in the first embodiment, the p⁺-typesemiconductor region PR is formed continuously along the Y axialdirection in each of the hybrid sub-cell regions LCh1 and LCh2.

<Method of Manufacturing Semiconductor Device>

A method of manufacturing the semiconductor device according to thepresent fourth embodiment is similar to the method of manufacturing thesemiconductor device according to the first embodiment described withreference to FIGS. 5 to 20 except that, in each of the hybrid sub-cellregions LCh1 and LCh2, the plurality of contact trenches CT are formed,and that the plurality of p⁺-type semiconductor regions PR are formed.

That is, in a step of manufacturing the semiconductor device accordingto the present fourth embodiment, in each of the hybrid sub-cell regionsLCh1 and LCh2, the plurality of contact trenches CT are arranged to bespaced from each other in the Y axial direction when seen in a planview. Also, in the step of manufacturing the semiconductor deviceaccording to the present fourth embodiment, in each of the hybridsub-cell regions LCh1 and LCh2, the p⁺-type body contact region PBCserving as a p-type semiconductor region is formed in a part of thep-type body region PB, the part being exposed to a bottom surface ofeach of the plurality of contact trenches CT. Also, the p⁺-type latch-upprevention region PLP is formed below each of the plurality of p⁺-typebody contact regions PBC. Thus, in the step of manufacturing thesemiconductor device according to the present fourth embodiment, in eachof the hybrid sub-cell regions LCh1 and LCh2, the p⁺-type semiconductorregions PR each including the p⁺-type body contact region PBC and thep⁺-type latch-up prevention region PLP are arranged to be spaced fromeach other in the Y axial direction when seen in a plan view.

In this manner, in the step of manufacturing the semiconductor deviceaccording to the present fourth embodiment, the plurality of contacttrenches CT arranged to be spaced from each other in the Y axialdirection when seen in a plan view are formed. Then, the plurality ofp⁺-type semiconductor regions PR arranged to be spaced from each otherin the Y axial direction when seen in a plan view can be formed whileusing the interlayer insulating film IL provided with the plurality ofcontact trenches CT as a mask. Thus, in the step of manufacturing thesemiconductor device according to the present fourth embodiment, it isnot required to prepare an additional mask for forming the plurality ofp⁺-type semiconductor regions PR, and it is not required to prepareadditional lithography for forming the plurality of p⁺-typesemiconductor regions PR.

<Main Characteristics and Effects of Present Embodiment>

In the semiconductor device according to the present fourth embodiment,as similar to the semiconductor device according to the firstembodiment, the p-type floating region PF included in the interpositionportion PR2 interposed between the two adjacent element portions PR1 isdivided into two by the two trenches 14.

Accordingly, in the present fourth embodiment, as similar to the firstembodiment, the gate capacitance can be increased, and the rapid changeor oscillation of current flowing in the IGBT at the time of turn-on canbe prevented or suppressed. Also, the IE effect can be enhanced, theon-voltage can be decreased, and the switching loss at the time ofturn-on in the L load switching can be decreased.

On the other hand, in the present fourth embodiment, as different fromthe first embodiment, the plurality of contact trenches CT are arrangedto be spaced from each other in the Y axial direction when seen in aplan view, and the p⁺-type semiconductor regions PR are arranged to bespaced from each other in the Y axial direction when seen in a planview.

As illustrated in FIG. 45, in the semiconductor device according to thefirst embodiment, in the hybrid cell region LCh, the p⁺-type bodycontact region PBC is formed continuously in the Y axial direction whenseen in a plan view, and the p⁺-type body contact region PBC in a partarranged at any position in the Y axial direction also contacts theemitter electrode EE. Thus, in the semiconductor device according to thefirst embodiment, the p-type body region PB in a part arranged at anyposition in the Y axial direction is also electrically connected to theemitter electrode EE via the p⁺-type body contact region PBC on thepart. Accordingly, as illustrated as a current path PT3 in FIG. 45, inthe semiconductor device according to the first embodiment, the holesare discharged to the emitter electrode EE also from the n⁻-type driftregion ND in a part arranged at any position in the Y axial direction inthe hybrid cell region LCh.

On the other hand, in the semiconductor device according to the presentfourth embodiment, in comparison to the semiconductor device accordingto the first embodiment, the plurality of contact trenches CT arearranged to be spaced from each other in the Y axial direction when seenin a plan view, and the p⁺-type semiconductor regions PR are arranged tobe spaced from each other in the Y axial direction when seen in a planview. Thus, as illustrated as the current path PT3 in FIG. 44, in thesemiconductor device according to the fourth embodiment, in the hybridcell region LCh, the holes are discharged to the emitter electrode EEonly from the n⁻-type drift region ND in a part arranged in the activesection LCba.

Thus, in the present fourth embodiment, hole discharge resistance ishigher than that in the first embodiment, the holes are easy to beaccumulated in a part of the n⁻-type drift region ND on the emitterelectrode EE side, an implantation efficiency of the electrons from theemitter electrode EE can be increased, and the IE effect can be furtherenhanced. Accordingly, in the present fourth embodiment, performance ofthe semiconductor device can be further improved than that in the firstembodiment.

Fifth Embodiment

In a fifth embodiment, the explanation is made about an example of amodule which has a plurality of semiconductor chips each including thesemiconductor device according to the first embodiment are included andin which the plurality of semiconductor chips are connected in parallelwith each other.

FIG. 46 is a circuit block diagram illustrating an example of anelectronic system using a semiconductor device according to the fifthembodiment. FIG. 47 is an equivalent circuit diagram illustrating amodule serving as the semiconductor device according to the fifthembodiment. FIG. 47 illustrates two IGBT modules 10 of six IGBT modules10 included in an inverter INV illustrated in FIG. 46, the two IGBTmodules corresponding to U-phase PH1.

As illustrated in FIG. 46, the electronic system using the semiconductordevice according to the present fifth embodiment includes a load such asa motor MOT, the inverter INV, a control circuit CTC1, and a controlcircuit CTC2. As such an electronic system, for example, a photovoltaicpower generation system, a wind power generation system, and anuninterruptible power supply (UPS) system are cited. As the motor MOT, athree-phase motor is used here. The three-phase motor is configured tobe operated by a voltage with three phases which are different from eachother. The control circuit CTC1 includes a plurality of power modulesPM1 and PM2.

In the electronic system illustrated in FIG. 46, an output of a powergeneration module (illustration is omitted) in, for example, thephotovoltaic power generation system, the wind power generation system,or the uninterruptible power supply system is connected to inputterminals TM1 and TM2 of the inverter INV, so that a direct-currentvoltage, that is, a direct-current power of the power generation moduleis supplied to the inverter INV.

The control circuit CTC1 is configured by, for example, an ECU(Electronic Control Unit), and has a semiconductor chip for control suchas an MCU (Micro Controller Unit) embedded therein. The control circuitCTC1 includes the plurality of power modules PM1 and PM2. Each of thepower modules PM1 and PM2 is also configured by, for example, an ECU,and has a semiconductor chip for control such as an MCU embeddedtherein.

Each of the plurality of power modules PM1 and PM2 included in thecontrol circuit CTC1 is connected to the control circuit CTC2. Theinverter INV is controlled by this control circuit CTC2. Althoughillustration is omitted, the control circuit CTC2 includes, for example,a gate driver and a photo coupler. The gate driver (illustration isomitted) included in the control circuit CTC2 is connected to theinverter INV. At this time, the gate driver (illustration is omitted)included in the control circuit CTC2 is connected to the gate electrodeof the IGBT provided in the inverter INV.

The motor MOT is connected to the inverter INV. A direct-currentvoltage, that is, a direct-current power supplied to the inverter INVfrom the power generation module (illustration is omitted) in, forexample, the photovoltaic power generation system, the wind powergeneration system, or the uninterruptible power supply system, isconverted into an alternate-current voltage, that is, analternate-current power by the inverter INV, and is supplied to themotor MOT. The motor MOT is operated by the alternate-current voltage orthe alternate-current power supplied from the inverter INV.

In the example illustrated in FIG. 46, the motor MOT is a three-phasemotor having U-phase PH1, V-phase PH2, and W-phase PH3. Thus, theinverter INV also corresponds to the three phases formed of the U-phasePH1, the V-phase PH2, and the W-phase PH3. Such an inverter INVcorresponding to the three phases totally includes six pairs of the IGBTmodule 10 and the diode module 11.

The semiconductor device according to the present fifth embodiment isequivalent to the IGBT module 10. Also, the IGBT module 10 includes aplurality of IGBT chips 12, and each of the IGBT chips 12 is equivalentto the semiconductor chip CHP (see FIG. 1).

In a case in which the motor MOT is a two-phase motor, note that theinverter INV totally includes four pairs of the IGBT module 10 and thediode module 11.

A part of the inverter INV, the part being closer to a power supplypotential VCC side than an input potential of the motor MOT, is referredto as a high side. Also, a part of the inverter INV, the part beingcloser to a ground potential GND side than the input potential of themotor MOT, is referred to as a low side. In the example illustrated inFIG. 46, three IGBT modules 10 are used as high-side IGBT modules 10,and three IGBT modules 10 are used as low-side IGBT modules 10. Also,three diode modules 11 are used as high-side diode modules 11, and threediode modules 11 are used as low-side diode modules 11.

A high-side IGBT module 10H out of two IGBT modules 10 corresponding to,for example, the U-phase illustrated in a region AR4 in FIG. 46,includes a plurality of, for example, six IGBT chips 12 each configuredby the semiconductor chip CHP as illustrated in FIG. 47. Also, alow-side IGBT module 10L out of the two IGBT modules 10 correspondingto, for example, the U-phase includes a plurality of, for example, sixIGBT chips 12 each configured by the semiconductor chip CHP. In both ofthe high side and the low side, the respective emitter electrodes EE ofthe plurality of IGBT chips 12 are electrically connected to each other,and the respective collector electrodes CE of the plurality of IGBTchips 12 are electrically connected to each other.

As each of the plurality of IGBT chips 12 included in the IGBT module10, the semiconductor device according to the first embodimentillustrated in FIGS. 1 to 4 can be used.

In the example illustrated in FIG. 46, in each phase of the three phasesformed of the U-phase PH1, the V-phase PH2, and the W-phase PH3, theIGBT module 10 and the diode module 11 are connected in antiparallelwith each other between the input potential of the motor MOT and thepower supply potential VCC supplied to the inverter INV via the inputterminals TM1 and TM2, that is, in the high side. Also, in each phase ofthe three phases formed of the U-phase PH1, the V-phase PH2, and theW-phase PH3, the IGBT module 10 and the diode module 11 are connected inantiparallel with each other between the input potential of the motorMOT and the ground potential GND, that is, in the low side.

The control circuit CTC2 is connected to the respective gate electrodesof the plurality of IGBT chips 12 included in the six respective IGBTmodules 10, so that each of the plurality of IGBT chips 12 included inthe six IGBT modules 10 is controlled by this control circuit CTC2. Notethat a plurality of diodes 13 are included in each of the six diodemodules 11, and each IGBT chip 12 and each diode 13 are connected inantiparallel with each other.

By controlling a current flowing in each IGBT module 10 by using thecontrol circuit CTC2, the motor MOT is driven and rotated. That is, bycontrolling on/off of each IGBT module 10 by using the control circuitCTC2, the motor MOT can be driven. When the motor MOT is driven asdescribed above, it is required to turn on and off the IGBT module 10.However, the motor MOT includes an inductance. Thus, when the IGBTmodule 10 is turned off, a reverse current which flows in a reversedirection to a direction in which the current in the IGBT module 10flows is generated by the inductance included in the motor MOT. The IGBTmodule 10 does not have a function to cause this reverse current toflow, and therefore, the diode module 11 is provided in antiparallelwith the IGBT module 10, so that the reverse current flows back torelease energy accumulated in the inductance.

<Main Characteristics and Effects of Present Embodiment>

As described above, the semiconductor device according to the firstembodiment can be used as each of the plurality of IGBT chips 12included in the IGBT module 10 serving as the module according to thepresent fifth embodiment.

Accordingly, also in the plurality of IGBT chips 12 included in themodule according to the present fifth embodiment, the gate capacitancecan be increased, and the rapid change or oscillation of the currentflowing in the IGBT at the time of turn-on can be prevented orsuppressed as similar to the semiconductor device according to the firstembodiment.

As described above in the first embodiment, note that the lower thecurrent flowing in the electronic system using the semiconductor deviceis, the easier the oscillation, that is, the ringing is observed at thetime of turn-on. Accordingly, when the electronic system using thesemiconductor device according to the present fifth embodiment is aphotovoltaic power generation system or an uninterruptible power supplywhich is an electronic system in which a lower current than a currentflowing in a wind power generation system flows, the effect ofincreasing the gate capacitance and preventing or suppressing the rapidchange or oscillation of the current flowing in the IGBT at the time ofturn-on is further enhanced.

Also in the plurality of IGBT chips 12 included in the module accordingto the present fifth embodiment, the IE effect can be enhanced, theon-voltage can be decreased, and the switching loss at the time ofturn-on in the L load switching can be decreased as similar to thesemiconductor device according to the first embodiment.

Note that each of the semiconductor devices according to themodification example of the first embodiment and the second to fourthembodiments can be used as each of the plurality of IGBT chips 12included in the IGBT module 10 serving as the module according to thepresent fifth embodiment. At this time, the plurality of IGBT chips 12included in the module according to the present fifth embodiment haveeffects that each of the semiconductor devices according to themodification example of the first embodiment and the second to fourthembodiments has, in addition to similar effects to effects that thesemiconductor device according to the first embodiment has.

In the foregoing, the invention made by the present inventor has beenconcretely described based on the embodiments. However, it is needlessto say that the present invention is not limited to the foregoingembodiments and various modifications and alterations can be made withinthe scope of the present invention.

What is claimed is:
 1. A method of manufacturing a semiconductor devicecomprising steps of: (a) preparing a semiconductor substrate including afirst main surface and a second main surface on an opposite side of thefirst main surface; (b) forming a first semiconductor layer of a firstconductivity type inside the semiconductor substrate; (c) forming asecond semiconductor layer of a second conductivity type different fromthe first conductivity type, inside a part of the semiconductorsubstrate, the part being located on the second main surface side withreference to the first semiconductor layer; (d) forming element portionsin the first semiconductor layer in two respective first regions of thefirst main surface of the semiconductor substrate, the two respectivefirst regions being arranged to be spaced from each other in a firstdirection when seen in a plan view; (e) forming an interposition portioninterposed between the two element portions formed in the two respectivefirst regions, in the first semiconductor layerm, in a second region ofthe first main surface of the semiconductor substrate, the second regionbeing located between the two first regions when seen in a plan view;(f) forming a collector electrode electrically connected to the secondsemiconductor layer; (g) forming a gate electrode electrically connectedto the two element portions; and (h) forming an emitter electrodeelectrically connected to the two element portions, wherein the step d)includes steps of: (d1) forming a first trench portion reaching a middleof the first semiconductor layer from the first main surface andextending in a second direction intersecting with the first directionwhen seen in a plan view, forming a second trench portion reaching amiddle of the first semiconductor layer from the first main surface,extending in the second direction when seen in a plan view, and arrangedon an opposite side of the second region side with reference to thefirst trench portion, and forming a third trench portion reaching amiddle of the first semiconductor layer from the first main surface,extending in the second direction when seen in a plan view, and arrangedon the second region side with reference to the first trench portion;(d2) forming a first trench electrode buried inside the first trenchportion via a first insulating film, forming a second trench electrodeburied inside the second trench portion via a second insulating film,and forming a third trench electrode buried inside the third trenchportion via a third insulating film; (d3) forming a first semiconductorregion of the second conductivity type contacting the first insulatingfilm and the second insulating film, on the first main surface side of apart of the first semiconductor layer, the part being located betweenthe first trench portion and the second trench portion, and forming asecond semiconductor region of the second conductivity type contactingthe first insulating film and the third insulating film, on the firstmain surface side of a part of the first semiconductor layer, the partbeing located between the first trench portion and the third trenchportion; and (d4) forming a third semiconductor region of the firstconductivity type contacting the first insulating film, on the firstmain surface side in the first semiconductor region, and forming afourth semiconductor region of the first conductivity type contactingthe first insulating film, on the first main surface side in the secondsemiconductor region, wherein the step (e) includes steps of: (e1)forming two fourth trench portions each reaching a middle of the firstsemiconductor layer from the first main surface, each extending in thesecond direction when seen in a plan view, and arranged to be spacedfrom each other in the first direction in the second region; (e2)forming two fourth trench electrodes buried inside the two respectivefourth trench portions via a fourth insulating film; and (e3) forming afifth semiconductor region of the second conductivity type in a part ofthe first semiconductor layer, the part being located between the twofourth trench portions, and forming two sixth semiconductor regions ofthe second conductivity type in the first semiconductor layer in thesecond region, wherein, in the step (e3), the two sixth semiconductorregions are formed in two parts of the first semiconductor layer, thetwo parts being located on both sides of the fifth semiconductor regionin the first direction via the two respective fourth trench portions,wherein in the step (g), the gate electrode is formed so as to be,electrically connected to the first trench electrode included in each ofthe two element portions, wherein, in the step (h), the emitterelectrode is formed so as to be electrically connected to the firstsemiconductor region, the second semiconductor region, the thirdsemiconductor region, the fourth semiconductor region, the second trenchelectrode, and the third trench electrode included in each of the twoelement portions, and so as to be electrically connected to the twofourth trench electrodes included in the interposition portion, andwherein an end portion, on the second main surface side, of each of thetwo sixth semiconductor regions is arranged on the second main surfaceside with reference to an end portion, on the second main surface side,of the fifth semiconductor region, in a third direction perpendicular tothe first main surface.
 2. The method of manufacturing a semiconductordevice according to claim 1, wherein, in the step (e3), the fifthsemiconductor region is formed when the step (d3) is performed.
 3. Themethod of manufacturing the semiconductor device according to claim 1,wherein, in the step (e1), two fifth trench portions are formed so as toreach a middle of the first semiconductor layer from the first mainsurface, extend in the second direction when seen in a plan view, and bearranged to be spaced from each other in the first direction between thetwo fourth trench portions, wherein, in the step (e2), two fifth trenchelectrodes are formed so as to be buried inside the two respective fifthtrench portions via a fifth insulating film, and wherein, in the step(e3), a seventh semiconductor region of the second conductivity type isformed in a part of the first semiconductor layer, the part beinglocated between the two fifth trench portions, and two eighthsemiconductor regions of the second conductivity type are formed in tworespective parts of the first semiconductor layer, the two respectiveparts being located on both sides of the seventh semiconductor region inthe first direction via the two respective fifth trench portions,wherein the fifth semiconductor region includes the two eighthsemiconductor regions, wherein, in the step (h), the emitter electrodeis formed so as to be electrically connected to the two fifth trenchelectrodes included in the interposition portion, and wherein an endportion, on the second main surface side, of each of the two sixthsemiconductor regions and the seventh semiconductor region is arrangedon the second main surface side with reference to both end portions, onthe second main surface side, of the two eighth semiconductor regions,in the third direction.
 4. The method of manufacturing the semiconductordevice according to claim 1, wherein the step (d) includes steps of:(d5) forming a sixth insulating film covering the first semiconductorregion and the second semiconductor region; (d6) forming a first openingportion penetrating the sixth insulating film and reaching a middle ofthe first semiconductor region, and forming a second opening portionpenetrating the sixth insulating film and reaching a middle of thesecond semiconductor region; (d7) forming a ninth semiconductor regionof the second conductivity type in a part of the first semiconductorregion, the part being exposed from the first opening portion, andforming a tenth semiconductor region of the second conductivity type ina part of the second semiconductor region, the part being exposed fromthe second opening portion; and (d8) forming a first connectionelectrode buried in the first opening portion, and forming a secondconnection electrode buried in the second opening portion, wherein animpurity concentration of the second conductivity type in the ninthsemiconductor region is higher than an impurity concentration of thesecond conductivity type in the first semiconductor region, wherein animpurity concentration of the second conductivity type in the tenthsemiconductor region is higher than an impurity concentration of thesecond conductivity type in the second semiconductor region, andwherein, in the step (h), the emitter electrode is formed so as to beelectrically connected to the third semiconductor region and the ninthsemiconductor region via the first connection electrode, and so as to beelectrically connected to the fourth semiconductor region and the tenthsemiconductor region via the second connection electrode.
 5. The methodof manufacturing the semiconductor device according to claim 1, whereinthe step (d) includes a step of: (d9) forming an eleventh semiconductorregion of the first conductivity type in a part of the firstsemiconductor layer, the part being located between the first trenchportion and the second trench portion and being located on the secondmain surface side with reference to the first semiconductor region, andforming a twelfth semiconductor region of the first conductivity type ina part of the first semiconductor layer, the part being located betweenthe first trench portion and the third trench portion and being locatedon the second main surface side with reference to the secondsemiconductor region, wherein the step (e) includes a step of: (e4)forming a thirteenth semiconductor region of the first conductivity typein a part of the first semiconductor layer, the part being locatedbetween the two fourth trench portions and being located on the secondmain surface side with reference to the fifth semiconductor region, and,wherein, in the step (e4), the thirteenth semiconductor region is formedwhen the step (d9) is performed.